1 1 

PHYSIOLOGY 
aEd HYGIENE 




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| MAYB ERRY | 






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COPYRIGHT DEPOSIT. 



PHYSIOLOGY 

AND 

HYGIENE 



BY 

JAMES W. MAYBEERY, A.B., A.M. 

professor of chemistry, epworth university, 

oklahoma city, oklahoma 

author of "physiology for young folks," 

"handbook of physiology" 



DALLAS, TEXAS 
THE SOUTHERN PUBLISHING CO. 

1910 






Copyright, 1908, 1910, by 
THE SOUTHERN PUBLISHING CO. 



©CI.A2734U0 



PKEFACE 

The success attending the publication of the author's 
Handbook of Physiology has encouraged him to prepare 
this volume. His close connection with instruction in 
physiology in public schools, county institutes, and normal 
schools peculiarly fits him for the preparation of such a 
work as this. 

While physiology is one of the oldest sciences known, 
it was one of the last to be included in the course of study 
for our common schools. Even after having been intro- 
duced as a formal subject it was not thought necessary to 
place it on the same thorough basis that characterized 
other subjects. The rapid and peculiar development of 
our modern high school course has made it impossible to 
include physiology as one of the university requirements. 
For this reason it must be completed by the pupils before 
they reach the high school. To teach it in a vague, in- 
definite, unscientific way is worse than not to teach it at all. 
The object of this work is to give the boys and girls a good 
knowledge of their bodies and to teach them how to protect 
these bodies from disease. 

As far as it has been consistent with clear treatment 
technical terms have been avoided, but the author is not 
one who believes that it is possible to teach physiology 
with the desired results without introducing a certain 
number of physiological terms. We might just as con- 
sistently try to teach grammar without the use of gram- 

iii 



IV PHYSIOLOGY AND HYGIENE 

matical phrases, or arithmetic without the introduction 
of mathematical expressions. And what are these but 
technical terms? Those words, names, and expressions 
only have been used, however, that are absolutely necessary 
to a good understanding of the subject. 

Only those theories that have been accepted by scientists 
in general have been advanced in this book. Allusions to 
illustrations of unusual cases or striking surgical operations 
have been studiously avoided in the main body of the 
work, as they tend only to confusion of mind. AVhere 
reference is made to anything of this nature, it is placed 
in a footnote. 

A sane presentation of the injurious effects of stimulants 
^and narcotics is included at the proper place. In discussing 
these subjects personal prejudices have been kept in the 
background. What boys and girls should be taught is the 
truth. A treatment that included the suppression of facts 
or exaggeration of truths would be disastrous in the long 
run. 

Believing that there is an education in a good drawing, 
the author has included a large number of illustrations 
which have been brought as close as possible to the sub- 
jects which they are to explain or illustrate. A consider- 
able number of the drawings have been made and engraved 
by the author in his own laboratory. 

The author desires to express his gratitude to the many 
kind friends who, by suggestion and encouragement, have 
materially aided in making this book possible. In con- 
clusion, he gratefully acknowledges the valuable assistance 
rendered by his wife in criticising and transcribing the 
manuscript from which the text -book has been printed. 



CONTENTS 



CHAPTER PAGE 

I. Introduction 1 

II. Cells 4 

III. Hygiene and Diseases ....... 9 

IV. Bones 14 

V. Skeleton 22 

VI. Cartilage and Connective Tissue .... 34 

VII. Muscles 39 

VIII. Hygiene of Muscles . 51 

IX. Organs of Circulation 65 

X. The Blood Vessels 74 

XI. The Blood 80 

XII. The Lymph — Narcotics 88 

XIII. Digestion — The Mouth 93 

XIV. Digestion — The Stomach 107 

XV. Digestion — The Intestines . . . . . .113 

XVI. Absorption . . . 126 

XVII. Metabolism 131 

XVIII. Foods 137 

XIX. Respiration 150 

XX. Diseases of the Lungs — Ventilation . . . 161 

XXL Excretion • . .169 

XXII. Bathing — Diseases 181 

XXIII. The Nervous System — The Brain .... 190 

XXIV. The Spinal Cord and Nerves 203 

XXV. Habit— Hygiene 216 

v 



vi CONTENTS 

CHAPTER PAGE 

XXVI. The Senses— Touch 224 

XXVII. Temperature, Muscular Sense, Taste, Smell . 234 

XXVIII. Hearing 242 

XXIX. Sight . . • . 252 

XXX. Stimulants .276 

XXXI. Narcotics 288 

XXXII. Poisons . . .290 

XXXIII. Tuberculosis 304 

XXXIV. "Catching" Tuberculosis 320 

XXXV. Recognizing and Curing Tuberculosis . . . 328 

Glossary . 339 



CHAPTER I 

INTRODUCTION 

Historical. — It may be of interest in entering upon 
the study of physiology to learn something of the origin 
and development of the word. Physiology is the oldest 
science known, having been taught by the ancients. 
The word physiology is made up of two Greek words, 
signifying "nature" and "discourse." Primarily, then, it 
means a discourse on, or talk about, nature. Origi- 
nally it included the study of what was then known of 
astronomy, physics, chemistry, botany, zoology, geog- 
raphy, etc. Gradually these phases of science have been 
taken up as separate studies until the term physiology 
to-day has an entirely different meaning from what it 
formerly had. Broadly speaking it includes the discussion 
of the structure and use of the parts of both plants and 
animals. We have, then, plant physiology and animal 
physiology. This text-book takes up only that portion of 
the latter subject which has to do with the human body. 

Terms Defined. — To understand fully what is said in 
the succeeding chapters we ought to know the meaning 
of various important terms that are used frequently in 
explaining the different subjects treated. With the object, 
of making the explanations clear we shall define the fol- 
lowing terms: physiology, anatomy, histology, hygiene, 
organ, function, tissues, membranes, mucous membranes, 
serous membranes, and glands. 

1 



2 PHYSIOLOGY AND HYGIENE 

Physiology treats of the structure of the body and the 
functions of its organs. 

Anatomy is the science that treats of the structure and 
form of the different tissues and organs of the body. 

Histology is the microscopic study of the various tissues 
that make up the body. In anatomy we tear the different 
organs apart and examine them as to their form, size, and 
relation to each other and to the whole body. Histology is 
a division of anatomy in which an examination is made 
of the minute structures through the microscope. Prac- 
tically, anatomy takes up the study of those parts that 
may be examined with the naked eye, while histology in- 
cludes only the microscopic study of the parts. 

Hygiene is the science of the care and health of the body. 
The object of making a study of anatomy and histology is 
to arrive at a good understanding of the structure and uses 
of the organs in order that we may know better how to 
care for them. 

An organ is a particular part of the body that has a 
function peculiar to itself or has some special work to do. 
The heart propels the blood, the muscles lift the arm, the 
stomach digests food, and the eye permits us to see. These 
are all organs. An organ, however, may have more than 
one function; for example, the tongue assists in mixing the 
food and aids in modifying the voice. 

The function of an organ is its special work, action, or 
use. The function of the ear is to hear. The function 
of the teeth is to chew the food. 

Tissues are the various substances or materials from 
which the organs or parts are made. Bone is made from 
osseous tissue, the brain from nervous tissue, while the 
heart is composed of muscular tissue. 



INTRODUCTION 3 

Membranes are thin sheets of tissue that cover organs, 
line tubes, or separate cavities. They are made up of 
sheets of fibers as in the tympanic membrane, or one to 
several layers of cells as in the mucous membrane of the 
alimentary canal. 

Mucous membranes are those that secrete a fluid which 
moistens the walls on which they are located. Mucous 
membranes line tubes or cavities that open out to the ex- 
terior of the body. The alimentary canal is lined its entire 
length by this kind of a membrane. 

Serous membranes are similar to the mucous, but they 
line the interior of the cavities that do not open out to the 
•exterior. The pleura and peritoneum are serous membranes. 

Glands are small pockets produced by the folding of a 
membrane. The membrane is usually made up of a single 
layer of cells; sometimes there are many pockets in a 
single gland. In such a case the gland is said to be com- 
pound. Glands usually open out upon a surface through 
a little tube called a duct. The function of a gland is to 
secrete a liquid. To do this it is necessary for the cells 
of the gland to come in close contact with the blood tubes. 
As the blood passes by, the cells take up the required 
material and pass it into the gland from which it flows out 
through the duct. The structures that secrete the saliva 
and gastric juice are true glands. 



CHAPTER II 



CELLS 



All Living Forms Composed of Organic Matter. — If we 
grind up a rock, a piece of glass, or a bit of iron, and put the 
powder under a microscope we find that it is made up of 
small portions not unlike in structure the large piece from 
which it was obtained. The various minerals with which 
we are familiar have been deposited by water or fused 
into their present form by extreme heat. If we take a 
thin section of either animal or vegetable matter and place 
it under the microscope we observe that it is composed 

entirely of many small rounded 
or irregular organs called cells. 

A Typical Cell. — The cells of 
which living matter is made up 
may vary in shape, size, and use, 
but all have certain things in com- 
mon so far as their structure is con- 
cerned. A typical cell is a mass of 
protoplasm, containing a nucleus, 
and surrounded by a cell wall. The 
cell wall is not always present, but 
when it is, it closely incases the 
jelly-like mass within. The proto- 
plasm, of which the body of the cell is made up, is an albu- 
minous substance composed largely of the four common 
elements, carbon, hydrogen, nitrogen, and oxygen. It is 

4 




Fig-. 1.— Diagram of a cell. 



CELLS 5 

in the protoplasm that rests that mysterious something 
called life. Within the cell is usually found a more con- 
centrated portion of the protoplasm, the nucleus, and 
sometimes within the latter is observed a still smaller por- 
tion known as the nucleolus. 

Cell Development. — There is an old idea held by certain 
people that " stones grow." This idea is incorrect, as 
stones never grow in the true sense of the word; neither 
do any other objects belonging to the mineral king- 
dom. They become larger only by additions to the out- 
side. The term "grow" can be used properly only in 
connection with living bodies. Out of the grain of corn 
emerges a sprout that grows into a mature stalk. From 
the egg comes the little chick that develops into the full- 
grown chicken. In plants and animals the growth is from 
the inside. It is of interest to inquire how this develop- 
ment takes place. 

Investigation on the part of scientists shows that from 
a comparatively small number of cells, frequently from 
a single cell, develops a body containing hundreds and 
thousands of cells. How does this 
increase come about? Careful obser- 
vation proves that it is the result of 
the "budding" of smaller cells on 
the parent cell or of the actual di- 
vision of the older cell into two parts 
which develop into complete, mature Fig. 2.— Budding yeast 
cells like the older ones. Just before 
the cell divides, it elongates, a portion of the nucleus 
moving toward each end. Gradually the cell contracts 
in the middle and finally separates altogether, giving 
rise to two complete cells. 




6 



PHYSIOLOGY AND HYGIENE 



Growth of Plant Life and Animal Life. — All living ob- 
jects, whether plant or animal, which are built up from cells 
are called organized matter. Science teaches us that there 
is no clear-cut distinction between animal life and vegetable 
life. If we pass down from the more highly organized bodies 
in both kingdoms to the lowest orders containing but one 
cell each it is a difficult task to determine whether a given 
single-celled structure is a plant or an animal. 

A common distinction between the animal and the plant 
is that the former has the power of motion and locomo- 
tion, while the lat- 
ter has not. This is 
not a true distinc- 
tion, however, as 
some plants are 
able to move about, 
while some animals 
do not have this 
power. Representatives of the latter class are certain 
species of the crinoids or "stone lilies" which attach 
themselves to the bottom of the sea, and do not move 
about as do most other animals. The diatom is a single- 
celled plant closely associated with the alga? in stagnant 
water. Under the microscope this sprightly little plant 
may be seen darting hither and thither with all the energy 
and activity of a little animal. 

In general, however, animals have the power of locomo- 
tion developed to a greater degree than have plants. For 
this reason we find animal tissue much more highly organ- 
ized than plant tissue. Since the motions of animals are 
more complicated and varied it is necessary that special- 
ized cells be developed in them to permit of these motions. 




Fig-. 3. — Diatoms. 



CELLS 



Kinds of Cells. — "While all the cells of an organized body 
arise from a single cell or a very few cells, yet, as a result of 




the specializing process just mentioned, they take on a 
variety of shapes and forms, dependent upon their particu- 
lar uses. Some cells are flat, as those of certain kinds of 
epithelium; especially in the outer portion of the skin, where 
protection is necessary. Some are elongated, as the muscle 
cells. Some develop into bone, becoming irregular in form, 
while others grow into cartilage, 
assuming a smooth globular ap- 
pearance. 

The blood is filled with mil- 
lions of regular disk-shaped 
cells whose function is to carry 
oxygen; besides these are a few 
irregularly shaped ones, having the power of locomotion 
and with various uses. A characteristic form is found in 
the trachea; these are columnar in shape with small hairs 
or cilia on the ends. In addition to these we have cells 
whose functions are: to secrete, as the cells of a gland; to 
excrete, as those of the sweat glands; to think and know 
and control, as those of the brain; each kind having its 
own peculiar shape. Others of lesser importance go to 
make up the whole of the human body. 




Nerve cells. 



8 



PHYSIOLOGY AND HYGIENE 



FOOD 
VACUOLE 



EXCRETORY ORGAN 



The Amoeba. — On account of its similarity to certain 
cells in the blood a word in regard to the amoeba may 
prove helpful. With some patience, this little animal may 
be found in stagnant water by the aid of the microscope. 
It is a single-celled structure, about one one-hundredth of 
an inch in diameter. It is composed of the usual proto- 
plasm, containing a nucleus 
but lacking a cell wall. It has 
the power to move from place 
to place by means of false feet. 
These feet are mere projec- 
tions thrown out from the 
main body of the cell. 

A projection is thrown out 
from one side of the cell, the 
protoplasm moves into this 
projection carrying the nu- 
cleus with it; the old portion 
now becomes the projection or 
"foot" which is drawn into the body. By a repetition of 
this process the amoeba is able to move slowly about in 
the water. Moreover, the amoeba has the power to wrap 
itself about food particles, digesting and absorbing them. 
It has the power to breathe in oxygen and eliminate waste 
matter. In fact, it has many of the powers possessed by 
man. The mature amoeba divides, forming two young ones. 




Amoeba. 



CHAPTER III 

HYGIENE AND DISEASES 

The Real Object of Instruction in Physiology. — Too often 
the main object of teaching physiology in our schools seems 
to be to give the young people a thorough course in anatomy 
and histology without any reference to the application 
of the knowledge that may be gained to the practical 
side of life. It is indeed a splendid thing for the boy 
or girl to know the location and structure of the lungs, 
but it is of far greater importance for him or her to un- 
derstand the true nature of those diseases that fasten 
themselves upon that structure with fatal results. It is 
well for the growing young man to understand something 
of the histology of the muscle fiber, but it is better for 
him to know the value of proper exercise to the develop- 
ment and growth of muscular tissues. 

It is the function of physiology to teach not only the 
structure and uses of the various organs of the body, but 
also the nature and character of diseases that are liable 
to attack these organs and the methods of preventing 
their attacks. Indeed, it is necessary to go beyond this 
and present some of the principles of sanitation, to the 
end that the body may be free from contaminating in- 
fluences that arise from unsanitary conditions found in 
many communities, villages, and cities. The old saying 
"an ounce of prevention is worth a pound of cure" is 
worth considering in connection with diseases. In teach- 

9 



10 PHYSIOLOGY AND HYGIENE 

ing physiology, too much emphasis cannot be placed upon, 
the proper care of the body. The knowledge the pupil gains 
of the different organs and structures should be made the 
basis for the development of hj'gienic laws, so that he may 
be able to ward off successfully the many encroachments 
of disease. 

Sanitary Conditions. — One of the greatest triumphs of 
modern science is the success it has achieved in overcoming 
the unsanitary conditions in many of our large cities, thus 
doing away in many cases with the causes of disease and 
reducing the number of deaths. 

Medical science has attacked the problem of yellow fever 
in Cuba and in the South, and while it has not been able to 
eradicate the disease entirely it has, by persistent and 
intelligent effort, been successful in reducing its ravages. 
The result of this effort inspires the hope that yellow fever 
will soon be a thing of the past. 

In most of our large cities where the streets and alleys 
were once filled with trash and filth of all kinds, they are 
now kept clean and free from any organic matter that 
might harbor disease germs. Sewage systems are built 
on more scientific principles, permitting the complete dis- 
charge of waste matter from the city limits. Refuse of 
every kind is carted away or burned up entirely. In many 
of our cities stringent ordinances have been passed by the 
council, providing a penalty for spitting upon the side- 
walk or floors of public buildings. These are some of the 
encouraging signs of the times that have grown out of the 
instruction in our public schools during the past few years. 

Conditions Still Far from Satisfactory. — While the ad- 
vance along the lines of sanitation has been great during the 
past quarter of a century, there remains much to be done. 



HYGIENE AND DISEASES 11 

Hidden from the public view in some of our great cities are 
accumulations of dirt and filth that annually give rise to 
epidemics of various kinds. The drinking water in many 
cases is impure and unwholesome. On account of the sur- 
roundings, the food even becomes unsanitary. 

In some of the smaller places and in the country small 
lakes and ponds of stagnant water, containing more or less 
organic matter, furnish breeding places for microbes of 
many kinds. The ditches and gullies by the street or 
road become filled with sluggish water and slime in which 
lurk millions of disease germs. Yards are heaped with 
refuse of every description, fragments of which are swept 
into well or cistern after every rain or freshet. The schools 
must teach the children and parents to see the necessity 
of better sanitary conditions in both city and country, 
so that they will not be content until every pond, every 
ditch, and every cesspool ceases to be a lodging place for 
bacteria and disease germs of any kind. 

Bacteria. — To understand the cause of many diseases it 
is necessary to know something about certain little vegetable 
structures called bacteria. These are small microscopic 
one-celled bodies, that live on organic matter and float 
about in the atmosphere. They vary in size and shape, but 
for any particular kind these are the same. Every germ 
disease is due to some special variety of bacteria. As has 
been suggested, bacteria thrive on decaying animal and 
vegetable matter. Indeed, it is thought that they are the 
cause of all decomposition, putrefaction, and fermentation. 

Xot all bacteria, however, are enemies of mankind; 
many of them work changes in the soil that are necessary 
to plant growth. They assist in breaking up and destroy- 
ing organic matter that otherwise would accumulate and 



12 PHYSIOLOGY AND HYGIENE 

become offensive. They even assist in bringing about some 
of the most important changes in connection with the 
human body. Many species of bacteria, then, are not only 
not harmful but are even necessary to health and to the full 
enjoyment of life. By a careful investigation, science has 
been able to classify the useful and the injurious varieties 
of bacteria. 

Disease Germs. — When bacteria or microbes get into the 
system and cause disease they are called disease germs. 
These gain access to the system through impure food or 
water, through the air we breathe, or through wounds or 
sores. Some of the diseases resulting from the attacks 
of bacteria are: typhoid fever, consumption, diphtheria, 
cholera, la grippe, erysipelas, smallpox, yellow fever, etc. 
Since the presence of these germs is liable to give rise to 
disease it is of the greatest importance that the body be 
kept in a strong and healthy condition in order that they 

may not find a suitable 
Oocoocoocq^ place to grow and in- 




. ^ 



25^ 



Fig. 7. — Bacteria. 



crease in number. The 
blood must be kept pure, 
the secretions regular, and 
digestion perfect, that the 
invading microbes may 
be met with all the 
strength of the different organs and destroyed before they 
gain a foothold anywhere in the system. 

Moreover, it is necessary that the breeding places of 
disease germs be removed. Decaying animal and vege- 
table matter should not be tolerated about the house or 
yard. Dust swept up from the floors should be burned. 
Dirt and filth and moisture should not be allowed to 



HYGIENE AND DISEASES 13 

remain or accumulate in storerooms or cellars. In fact, 
cleanliness should be the daily watchword in every home. 
Then, too, if there is any reason to suspect the presence of 
disease germs on account of sickness in the vicinity, or for 
any other reason, the home should be thoroughly fumi- 
gated to destroy any microbes that may have found their 
way into the house. 

Hygiene in General. — We have just discussed the relation 
between certain diseases and the germs that cause them. 
A word concerning the general care of the body may not 
be out of place here. Our Creator has given to the most 
of us a strong, healthy, vigorous body. It should be our 
pleasure as well as our duty to protect it from the ravages 
of disease and accident as far as it lies within our power. 
What is finer to look upon than an erect, sturdy, sinewy, 
well-developed human figure? Who is more to be pitied 
than the owner of a stooped, hollow-breasted, sunken- 
cheeked, sallow-faced body ? It is the function of physiol- 
ogy to discuss fully the structure and uses of the different 
organs of the body, and in addition to lead the student to 
know how to keep these organs in a healthy condition to 
the end that he may enjoy the fullness of health and the 
blessing growing out of the same. 



CHAPTER IV 

BONES 

Osseous Tissue. — Osseous tissue is the tissue of which 
bone is made. As most buildings have a framework 
around which is arranged the material that goes to make 
up the edifice, so the human body has a framework that 
supports its other tissues. The skeleton is not a single, 
rigid piece of osseous tissue, but is composed of a large 
number of portions of this tissue called bones. These are 
of many shapes and sizes, and are connected by means 
of joints and articulations into a perfect whole, strong 
and substantial, yet susceptible of varied and graceful 
motions. 

When connected by tendons and ligaments and covered 
by muscle and tissue and fiber the skeleton helps to form 
the most remarkable piece of mechanism found in nature. 
To learn something of the use of bones and of the 
skeleton made from them, it is necessary to study the 
origin, composition, and structure of osseous tissue, the 
relation of bones to each other and to the skeleton as a 
whole. 

Origin of Bone. — By extended research along the line it 
has been discovered that bone originates in two different 
ways. It may be deposited from membranes, in the form 
of plates or sheets, or it may be preceded by cartilage into 
the substance of which the bony tissue is built, the carti- 
lage being gradually carried away. 

14 



BOXES * 15 

Membrane Bones. — A typical form of this class of bones 
is found in the bony shell inclosing the cranial cavity. If a 
microscopic examination of the membrane surrounding the 
cranial cavity be made before the osseous matter is deposited 
small cells may be seen arranged along under the membrane. 
At the proper time these cells begin the deposit of the real 
bone tissue or mineral matter in connection with a certain 
amount of animal matter. In building in the osseous tis- 
sue the cells draw their supply of material from the blood; 
the membrane contains a large number of blood vessels. 
When the bone has matured the membrane from which it 
was deposited becomes the periosteum. Since they help to 
form the bone, these bone builders are called osteoblasts, a 
term meaning bone germs. 

Cartilage Bones. — As already stated cartilage bones are 
those that replace cartilage. In the infant, at the proper 
place, is developed a mass of cartilage having the same size 
and shape as the bone which is to follow. Covering the 
cartilage is a thin membrane under which may be found 
many of the osteoblasts just mentioned in connection with 
membrane bones. Distributed among the osteoblasts are 
found other large cells that perform a peculiar duty. 

When it is time for the so-called ossification to set in, 
these large cells bore their way down into the cartilage 
for a certain distance and then continue their course lon- 
gitudinally with the cartilage, tearing it away as they go. 
Blood vessels grow into the little tubes burrowed out by 
the cells, after which the smaller osteoblasts follow, taking 
the osseous tissue from the blood and building it in as a 
bony lining to the tubes. In this way the cartilage is 
gradually torn down and carried away and bone is deposited 
in its place. Even after the bone is completely formed 



16 



PHYSIOLOGY AND HYGIENE 



these cells remain to assist in repairing the bone in case 
of fracture or disease. 

Since the large cells were first observed tearing down 
bone instead of cartilage the} 7 were called osteoclasts, a 
term meaning bone breakers. Frequently these cells be- 
come lodged in the small bony cavities and are known as 
common bone cells. Though imprisoned within the bony 
walls they seem to have something to do with the nourish- 
ment of the bone. After the cartilage has disappeared, 
its original covering remains as the periosteum. 

Gross Structure of Bone. — If a live bone be examined on 
the outside it will be found covered with a tough vascular 
membrane called the periosteum, a membrane already 
mentioned in connection with the origin of bone. The 
membrane adheres to the bone closely at every point ex- 
cept at the joints, which are covered by a thin, smooth 

layer of cartilage. The peri- 
osteum is richly supplied with 
blood vessels. It does not 
nourish the bone directly, but 
carries the blood vessels which 
furnish the material for nour- 
ishment. However, the peri- 
osteum is necessary to the life 
and growth of bone. It fur- 
nishes a home to the osteo- 
blasts which lie under it in 
great numbers, and supplies 
the material for -their use. 
Diseased bone from which the periosteum has been re- 
moved cannot be reproduced. 

As already stated the joints of bones are covered with a 



CANCELLATED. 




Fig. 8. 



SOLID TISSUE 



Section of upper end of 
femur. 



BONES 17 

smooth cartilage which permits of movements between the 
bones without much friction. If we cut a long bone 
crosswise about the middle we shall observe that it is 
tubular in form, its walls being made up largely of hard 
compact bony tissue. The 1 tube contains a yellow fatty 
tissue called the yellow marrow. This is crowded into 
the tube tightly and serves to break any shocks to which 
the bone may be subjected and at the same time to give 
strength and lightness to the bone. This tube is called 
the medullary canal. Surrounding the marrow and lining 
the canal is a membrane called the endosteum, whose 
function is similar to that of the periosteum. 

Toward the ends of the bone, which are usually en- 
larged, the hard compact tissue gives way to a spongy 
bone which is so constructed that it gives both lightness 
and strength. This is the cancellated bone, in the spaces 
of which is found a reddish substance known as red 
marrow. A thin sheet of cancellated bone is developed 
between the endosteum and the compact tissue of the bone 
shaft. As they develop long bones become hollow so that 
they may be strong and at the same time not unwieldy. 
In short, flat, and irregular bones the medullary cavity is 
lacking and the tissue is largely cancellated. 

Histology of Bone. — Under the microscope a cross 
section of compact bone shows small openings or tubes 
which are called Haversian canals. Arranged around these 
canals are concentric layers of bony tissue called lamellae, 
between which are small irregular openings, the lacunae, 
— a term meaning a small opening. Radiating from the 
lacunae and connecting one lacuna with another are very 
small tubes or canals, called canaliculi. 
1 See page 21, footnote. 



18 



PHYSIOLOGY AND HYGIEXE 




If one were to examine a longitudinal section of the same 
bone he would find that the Haversian canals run lengthwise 
of the bone, but frequently they are found to run obliquely, 
one uniting with another. In this way the whole Haver- 
sian system is in communi- 
cation with the periosteum 
and the endosteum. Run- 
ning into the Haversian 
canals from these two 
membranes are blood ves- 
sels, nerves, and lymphat- 
ics which nourish the osse- 
ous tissue. Lodged in the 
lacuna? are the nucleated 
bone cells already men- 
tioned as being impris- 
oned osteoblasts. 
Composition of Bone. — If the bone of a child be ex- 
amined it is found to contain a large per cent, of an albumi- 
nous substance commonly called animal matter. This is 
probably some of the cartilage which has not yet been re- 
placed with bone. If the bone of an adult be analyzed it is 
found to contain about thirty-five per cent, animal matter 
and sixty-five per cent, mineral matter. The animal matter 
is, strictly speaking, ossein, which, being boiled, changes 
into the familiar substance known as gelatine. The mineral 
matter is made up of the following compounds : calcium phos- 
phate, fifty; calcium carbonate, ten; calcium fluoride, two; 
magnesium phosphate, one; and other salts, two per cent. 
The animal matter of bone may be entirely removed by 
burning the bone for some time in the fire of an ordinary 
stove. The bone first turns black upon being heated, but 



Fig. 9. —Haversian canals, 



BONES 



19 



after a while it changes to a clean white. It is now very 
brittle and can easily be crushed with the fingers. The min- 
eral matter may be taken out by soaking the bone for sev- 
eral days in strong vinegar, or, better still, in weak muriatic 
acid. If a long 7 slender bone be thus treated, it becomes 
pliable and may be easily bent or perhaps tied into a knot. 

Joints, or Articulations. — The different bones of the 
body are united by means of joints to make up the skeleton. 
These articulations are so arranged 
as to give strength and rigidity to 
the parts or permit of movement be- 
tween the bones with as little fric- 
tion as possible. In the case of a 
juncture that allows motion, the ends 
of the bones that rub together are 
covered with a smooth layer of car- 
tilage which serves as an elastic cush- 
ion to break shocks and to permit 
of easy movement. Lining the cavity 
of the joints is the synovial mem- 
brane which secretes a glairy mucilag- 
inous fluid called the synovial fluid 
or synovia. This lubricates or oils 
the joint and takes its name from its likeness to the white 
of an egg. 

Kinds of Joints. — Joints are of two general kinds, 
movable and immovable. The motion in movable joints 
is permitted in several ways. The knee and elbow joints 
as well as those between the phalanges and a few others 
permit of a motion similar to that of a knife blade on its 
handle and are called hinge joints. In the shoulder and 
in the hip we have illustrations of joints made up of a 




Fig-. 10. — Hinge joint of 
the elbow. 



20 



PHYSIOLOGY AND HYGIENE 



globular projection on the end of one bone fitting into a 
hollow cup or depression in another. These are known as 
ball and socket joints. A specialized joint is that between 
the axis and the atlas at the top of the backbone. A peg 
on the axis fits into an opening in the atlas above, permit- 
ting of a rotary motion. This is called a pivot joint. Ar- 
ticulations in which the bones move over each other with 
but little freedom, as between the carpal bones, are called 
gliding joints. 

The immovable joints are found largely in the head. 

The bones of the 
0m cranium fit into 

each other in a pe- 
culiar dovetailed 
fashion and are 
styled suture 
joints. The artic- 
ulations between 
the vertebrae of 
the backbone are 
sometimes called 
mixed joints since 
they allow motions 
of various kinds. 
Connection of Joints. — Bones are held together at the 
i movable joints by means of strong, tough cords or sheets 
of connective tissue, called ligaments. These are so ar- 
ranged as to permit of the required motion and yet hold 
the parts firmly together. This arrangement is especially 
noticeable in the wrist, where great freedom of motion is 
possible in connection with a high degree of strength. In 
joints where little if any motion is possible, the bones are 




Fig-. 11. — Ball and socket joint at the hip. 
(Drawn apart showing ligament attachment.) 



BONES 21 

connected by layers or pads of cartilage. These tend to 
break any jars or shocks to which the body may be sub- 
jected. A nice arrangement of this kind is observed in 
the backbone, where the rings of cartilage give a certain 
degree of elasticity to the spine and allow the brain to be 
carried with but little danger of shock from walking. 

Footnotes. — 'Ina man weighing 150 pounds, the different parts 
of the body weigh about as follows: Muscles, 65; bones, 24; fat, 28; 
skin, 10; organs of the thoracic and abdominal cavities, 13; blood, 
17; and the brain, 3 pounds. 

2 Experiments have shown that the body is from an eighth to a 
quarter of an inch taller in the morning than at night. During 
the day the weight of the body compresses the pads of cartilage 
between the vertebrae and the height is diminished. While lying 
down at night these pads resume their normal thickness; as a result 
the body is longer when one arises in the morning. 

3 The bones of birds are hollow and filled with air. This arrange- 
ment makes them light and permits the birds to fly more easily. 



CHAPTER V 

SKELETON 

Uses of Skeleton. 1 — The skeleton is built up of bones 
and forms the framework of the body. It furnishes a basis 
for the attachment of muscles, and under their action per- 
mits of motion and locomotion. It assists in forming cav- 
ities and helps protect the softer and more delicate tissues 
and organs of the body. 

The Skull. — The skull is the bony part of the head and 
is made up of the upper rounded portion, the cranium, and 
the lower, front, irregular portion called the face. There 
are altogether twenty-eight bones in the head — eight cra- 
nial bones, fourteen facial bones, and six ear bones. The 
cranial cavity, which contains the brain, is composed of the 
occipital at the back and base, two parietal or wall bones 
at the upper side to the back, two temporal at the lower 
side to the front, the frontal in the forehead, the sphenoid 
below and to the front of the occipital, and the ethmoid, 
in front, just back of the eyes. 

The sphenoid, a heavy shaftlike bone, is one of the 
most irregular bones in the body, and passes through the 
lower part of the cranium, locking and binding the other 
bones into a substantial whole. 

The face is made up of the following bones: two nasal 
or nose bones, two lachrymal or tear bones, two superior 
maxillary, two malar or cheek bones, two turbinated, two 
palatals, one vomar, and one inferior maxillary. 'Each 

1 See page 21, footnote. 
22 




Fig-. 12. — The skeleton. 
- 23 



24 



PHYSIOLOGY AND HYGIENE 



ear contains three small bones called the stirrup, hammer, 
and anvil. The os hyoides or hyoid bone hardly belongs 
to the skull proper, but is mentioned here since to it is 
fastened the base of the tongue. 

Two projections or processes are prominent in connection 
with the skull. The zygoma or zygomatic arch is a slender 
projection of the malar extending back from the cheek, 
meeting a like projection from the temporal bone. The mas- 
toid process is found at 
each side of the base of 
the skull and protects 
the delicate organs of 
the bony ear. 

At the base of the 
skull is found one of the 
largest foramina in the 
body. This is an open- 
ing in the occipital bone 
called the foramen mag- 
num or great foramen, 
through which the spi- 
nal cord enters the cra- 
nium. 

It has already been 
stated that the cranial 
bones articulate by 
means of suture joints. 
These are made up of 
serrated or saw-toothed edges that fit into each other in 
such a way that a firm wall is formed, yet so that shocks 
cannot easily be transmitted across these sutures from one 
If the cranium were a solid bone, . a 




Fig. 13. — The skull. 
1, frontal bone; 2, parietal bone; 3, tem- 
poral bone ; 4, sphenoid bone ; 5, malar 
bone; 6, superior maxillary (upper jaw) 
bone; 7, occipital bone; 8, inferior 
maxillary (lower jaw) bone; 9, nasal 
bone; 10, ethmoid bone; 11, lachrymal 
bone. 



bone to the other. 



SKELETON 



25 



04 



CERVICAL 



.THORACIC v 
f(OR DORSAL) 



shock received at one point would be transmitted to every 
portion of the surface of the brain and death would prob- 
ably be the result. 

Frequently, the cranial 
bones do not develop com- 
pletely, leaving small spaces 
between them called fonta- 
nelles. A large fontanelle 
at the top of the cranium, 
called the soft spot, very 
often remains until late in 
life. Sometimes little bones 
develop in these fontanelles 
to which the name Wormian 
has been given. 

The Trunk.— The trunk is 
composed of the spine or back- 
bone, the shoulder girdle, the 
ribs, and the pelvic girdle. 
It constitutes the main part 
of the body and helps form 
two large cavities, the tho- 
rax or chest and the ab- 
domen, separated by a mus- 
cular sheet, the diaphragm. 

The Backbone. 1 — The 
backbone is not a single 
bone, but is made up of 
twenty - four vertebrae, the 
sacrum and the coccyx. A 
vertebra is an irregular mass 

b Tig. 14. — The vertebral column 

1 See page 21, footnote. as seen from the side. 



rz 



01 



^LUMBAR, 



V SACRAL 



26 



PHYSIOLOGY AND HYGIENE 



of bone composed of a solid portion called the centrum, 
from which the neural arch extends backward forming the 
neural ring, a hole through which the spinal cord passes- 
Projecting backward and usually downward is the spinous 
process. These processes may be felt by rubbing the hand 
down the middle of the back. Projections running out 
from each side of the vertebra are called transverse proc- 
esses. The vertebrae are connected by means of pads of 
cartilage placed between them to deaden shocks, and 
articulate by means of smooth bony faces or facets. 

The vertebrae are classified as cervical, dorsal, and lumbar, 
each division being numbered from the top. The first two 
cervical vertebrae have already been mentioned as the atlas 
and axis, there being seven in all. The second division, 
the dorsal, include twelve, and the lumbar, five ver- 
tebrae. Below the lumbar verte- 
brae are the sacrum and the 
coccyx, single bones made up of 
smaller bones fused together. 

When these irregular spiny 
bones are put together and bound 
by means of cartilage and liga- 
ments, they form a tapering 
column that is strong and sub- 
stantial, yet yielding and elastic, 
permitting of those varied and graceful motions of which 
the human body is capable. The neural rings of the 
several vertebrae form a long continuous tube through 
which runs the delicate and sensitive spinal cord. 

The Shoulder Girdle. — A ring of bones extending around 
the shoulder, giving it strength and solidity, is called the 
shoulder or pectoral girdle. It is composed of two scapulae, 




Fig. 15. — Sixth thoracic ver 
tebra, as seen from above. 



SKELETON 



27 



two clavicles, and one sternum. The scapulae are imbedded 
in the flesh in the back of each shoulder as broad flat bones 
and are commonly called the shoulder blades. Articulating 
with the scapulae on the inner side of the front are two sub- 
stantial rodlike bones called the clavicles. These articulate 
with the upper part of the sternum at a middle point below 
the neck and serve as braces to strengthen the shoulders. 
These are called the collar bones. 

On each scapula at the upper outside of the shoulder is 
a prominent process called the acromion. A similar proc- 
ess, known as the coracoicl, extends inward from the same 
point on the scapula. These two processes with the clav- 
icle form a depression 
or cavity called the 
glenoid cavity; this is 
the socket of the 
shoulder into which fits 
the ball Of thehumerus. 

The Ribs.— The ribs 
are long, flat, curved 
bones, twenty-four in 
number, which articu- 
late with the backbone, 
and, curving to the 
front, inclose the thora- 
cic cavity. These are ar- 
ranged in pairs, twelve 
in number. The first 
seven pairs articulate 
with the long vertical bone already mentioned, the sternum, 
and are called the true ribs. The last five pairs do not 
articulate with the sternum directly and are called false 




Fig. 16. — Articulation of ribs to a 
vertebra. 

t, transverse process; v, centrum of vertebra ; 
r, rib; c, costal cartilage; s, sternum. 



28 



PHYSIOLOGY "AND HYGIENE 



ribs. The first three pairs of false ribs are connected with 
each other and the sternum by means of bands of car- 
tilage. The ribs are so formed and arranged that under 
the influence of the muscles the capacity of the thorax 
can easily be changed. The ribs assist in protecting the 
delicate organs lying within the body. 

The Pelvic Girdle. — This girdle is composed of the large 
wing-shaped innominate bones — one on each side — and the 

sacrum already 
mentioned. The 
pelvic girdle is 
rigid, compact, 
and massive, be- 
ing constructed 
to bear the great 
weight of the 
body, and to 
withstand any 
shocks to which it 
may be subject- 
ed. The two in- 
nominate bones 
are extended to 
the back, where 
the sacrum is 
wedged in tightly 
between them. Tn the lower part of each innominate bone 
is the largest foramen in the body, called the thyroid fora- 
men. In the side of each innominate bone is a depression 
or hollow called the acetabulum. This is the hip socket into 
which the bail or head of the femur fits. 

The Upper Extremities. — Each upper limb includes the 




-Front view of the pelvis, with its 
ligaments. 

innominate bone; b, crest of ilium; c, sacrum; d, 
pubes; e, anterior sacroiliac ligament; /, iliofemo- 
ral ligament; g, obturator membrane; h, sym- 
physis pubis; i, sacrosciatic ligament; /, anterior 
common ligament. 



SKELETON 



29 



HUMERUS 



arm, the forearm, and the hand. The arm is composed of 
the humerus, a long, slender bone articulating with the 
scapula by means of a ball and socket joint and with the 
forearm by means of a hinge 
joint. The forearm is made 
up of two long slender bones 
called the radius and ulna, 
the former being small at the 
elbow and large at the wrist, 
the ulna being small at the 
wrist and large at the elbow. 
A process of the ulna extends 
back under the humerus and 
forms at the elbow the olecra- 
non process or crazy bone. 
The radius and ulna are so ar- 
ranged as to permit of a free 
rotary motion of the fore- 
arm. 

The hand includes the wrist, 
the palm, and the fingers. 
The wrist is made up of eight 
small irregular bones called 
the carpals. Extending out- 
ward from the carpals and 
forming the palm are five 
slender bones commonly called 
the metacarpals. At the ex- 
tremities of the metacarpal 
bones are the small oblong 
bones of the fingers, the pha- 
langes. Each finger has Fig. 18. — Upper limb bones. 



VlETACARPU 



PHALANGES 




RADIUS 



INTEROSSEOUS 
SPACE 



METACARPUS 



PHALANGES 



30 



PHYSIOLOGY AND HYGIENE 



three phalanges with the exception of the thumb which 
has but two. 

Frequently, when bones are subjected to much friction 
there is a growth of osseous tissue on the bone similar to 
the development of a corn on the skin. These small 

growths are called sesamoid 
bones. They often grow 
on the inner side of the 
joints of the forefinger and 
the thumb. The shallow 
socket of the shoulder, the 
freedom of motion of the 
radius and ulna, the glid- 
ing movements of the 
wrist, and the suppleness 
of the fingers all combine 
to adapt the upper limbs 
to the many nice and sinu- 
ous motions so necessary to 
the full use of those parts. 
The Lower Extremities. 
— Each lower limb includes 
the thigh, the calf, and the 
foot. The thigh bone, called 
the femur, articulates with 
the pelvis by means of a 
ball and socket joint. It is a 
long slender bone similar to the humerus, having at its upper 
end on the outer side a projection or process, called the great 
trochanter. The calf of the leg is made up of the tibia and 
the fibula, the former of which is much the larger, the fibula 
acting more as a brace than a part of the real framework. 




Fig. 19. 



Carpals, bones of the 
hand. 



<s, scaphoid; I, lunar; Pd, pyramidal; 
Pm, pisiform; tm, trapezium; t, 
trapezoid; o, os magnum ; u, 
cuneiform : m, metacarpals; c, 
phalanges. 



SKELETON 



31 



•^ 



INNOMINATE 



FEMUF 



The ends of the bones at the knee are much enlarged to 
furnish surface for the attachment of muscles as well as to 
provide a leverage for the 
action of the same. To in- 
crease this leverage and to 
give an easy support for the 
body when resting on the 
knee a specialized sesamoid 
bone is developed in the 
ligaments of the knee joints, 
called the knee-cap or patella. 

The bones of the foot are 
much like those of the hand. 
Those of the ankle and heel 
are called the tarsals and 
are seven in number. Ex- 
tending forward, forming 
the arch of the foot, are the 
five metatarsals. In each 
toe are three phalanges with 
the exception of the great 
toe, which contains but two. 
The deep socket at the hip, 
the massive joint at the 
knee, the substantial ar- 
rangement of the tibia and 
fibula as well as that of the 
tarsals give to the lower 
limb strength and firmness. 
The arch-shaped structure 
of the foot gives to it springi- 
ness and elasticity. 



PATELLA- 



FIBULA 
INTEROSSEOUS 



TIBIA 



METATARSUS 



PHALANGES/ 



-TARSUS 



-METATARSUS 



PHALANGES 



Fig-. 20. — Lower limb bones. 



32 



PHYSIOLOGY AND HYGIENE 



Rickets. — As has already been stated, the bones are 
nourished by blood vessels which traverse the Haversian 
system. In childhood they are comparatively soft, but 
the cartilage is gradually replaced by mineral matter de- 
posited by the osteoblasts 
from the blood. If for any 
reason this mineral matter is 
not deposited the bones do 
not harden rapidly enough 
to sustain the weight of the 
body. In a case of this kind 
other conditions are usually 
present which cause an ab- 
normal development of the 
head and upper part of the 
body while the lower limbs 
remain undeveloped. As a 
result the legs become dis- 
torted and are hardly able 
to bear the weight of the 
body. The cranial bones are 
soft, the eyes roll in their 
sockets, while the large head 
lolls on the shoulders. Usu- 
ally the brain is affected, 
preventing a proper devel- 
opment of the mind. Such 
a disease is called rickets. 
To prevent it, food contain- 
ing a sufficient amount of mineral matter should be eaten 
and plenty of exercise taken. 

Hygiene of Bones. — Since the shape of a bone, when 




Fig. 21. — Tarsals, bones of the 
foot. 

a, astragalus; e, calcaneum; h, cu- 
boid; c, external cuneiform; m, 
middle cuneiform ; ec, internal cu- 
neiform; n, navicular; t, metatar- 
sals; p, phalanges. 



SKELETON 33 

once determined, cannot easily be changed, it is of great im- 
portance that it should not be subjected to great weight or 
strain until it be matured. Very young children should not 
be encouraged to walk until the bones are strong enough to 
bear the weight of the body. Many cases of bow-leggedness 
are due to the premature efforts on the part of the children 
to walk. Since bones are not fully matured until the chil- 
dren are grown, the boys and girls should be taught to walk 
straight, and hold the shoulders back while sitting. 

Continual bending over the .desk may produce a perma- 
nent distortion of the spine that will make the pupil hump- 
backed or round-shouldered for life. Many young people 
perform their tasks with one shoulder higher than the other, 
thus producing a permanent curvature of the spine. Tight 
clothing and tight shoes tend to deform the bones to such an 
extent as to result in an unsightly body, awkward gait, 
and ill health in general. As already stated, children should 
be furnished food containing plenty of nourishment for the 
bones. They should be taught to take proper exercise to 
the end that a skeleton may finally be developed that will 
prove a strong and substantial framework for the support 
of the other tissues of the body. 



CHAPTER VI 

CARTILAGE AND CONNECTIVE TISSUE 

Cartilage. — We have just discussed at length one kind 
of supporting tissue called bone. We shall now describe 
briefly a tissue similar, in some ways, to bone, yet differing 
from it in both structure and use. We have already men- 
tioned the fact that the size and shape of most bones are 
determined in advance by a substance called cartilage, and 
that this substance is finally torn down and replaced by 
osseous tissue. Cartilage, however, is found in various 
parts of the body in the mature individual and has a 
structure and function peculiar to itself. It is similar to 
bone inasmuch as it is tough and frequently becomes 
calcified. The difference in the structure of bone and 
cartilage, however, is so marked that it is not difficult to 
distinguish the one from the other. 

We have already learned that bones have a system of 
canals and canaliculi running through them that are filled 
with blood vessels, nerves, and lymphatics. These Haver- 
sian canals and canaliculi are entirely lacking in cartilage, 
consequently there are but few, if any, blood tubes in the 
same. Bone cells are irregular and much branched while 
cartilage cells are rounded, smooth, and not branched. 
Mature bones are unyielding and rigid while cartilage is 
usually quite flexible. We frequently speak of bone as 
containing a greater per cent, of mineral matter than 
cartilage. Although this is ordinarily the case, yet often 

34 



CARTILAGE AND CONNECTIVE TISSUE 35 

the reverse is true, cartilage having a greater amount of 
mineral matter than bone. 

Kinds of Cartilage. — Cartilage is very much alike wher- 
ever found in the body in that it is tough and flexible. 
Nevertheless, it differs sufficiently in structure to adapt 
it to its various uses. According to its structure and color, 
cartilage is divided into three general classes : hyaline, yel- 
low elastic, and white fibrous. 

Hyaline. — This kind of cartilage is sometimes referred 
to as true cartilage or gristle and is pale blue in color. 



%k, 



4d , .. - 



m* 



.# 




i inilim «i in ■ J y^^^^^rrrinr 

BONE 

Fig. 22.— Hyaline cartilage. Fig-. 23. —Yellow elastic cartilage. 

It consists of a tough gelatine-like substance in which 
are imbedded small roundish cells. As the name im- 
plies, it is practically without fibers. It is translucent 
and firm and but slightly elastic. Its structure admirably 
adapts it for use where a smooth, articulating surface is 
required, hence it is found regularly at the ends of bones. 
Yellow Elastic. — As hyaline cartilage is sometimes 
called true cartilage so yellow elastic is often referred to as 
false cartilage. Here we have a tissue made up of cells 



36 



PHYSIOLOGY AND HYGIENE 



lodged in a web of very densely packed yellow elastic fibers. 
The cells are inclosed in the meshes of the yellow fibers. 
The elasticity of this cartilage is doubtless due to the fact 
that it is made up of slender wavy threads. The structure 
of yellow elastic cartilage renders it especially suitable 
for use where both toughness and elasticity are desirable 
and where a change of form is necessary. For this reason 
it is found in the larynx, external ear, tip of nose, etc. 
Both the nose and the ear are located where they are 
liable to be broken or torn off, hence the necessity of a 
structure both tough and flexible. 

White Fibrous. — In structure, white fibrous cartilage is 
very much like yellow elastic. The cells are packed in 
a closely pressed mass of white fibers. Here, however, 
instead of the fibers being wavy and elastic, they are 

straight and inelastic, being woven 
together in such a way, though, as 
to make the cartilage somewhat 
pliable. White fibrous cartilage is 
found in the form of disks, between 
articulating bones, in bands or 
sheets called ligaments, and as a 
lining for bony grooves in which 
tendons of muscles glide. Yellow 
elastic cartilage and white fibrous 
cartilage are sometimes included 
under the general term of fibro- 
cartilage since both are composed 
largely of fibers. 
Connective Tissue. — It has been pointed out that there 
are well-defined differences in the structure of bone 
and cartilage, but an attempt to draw a clear-cut distinc- 




KzZ 



■ U 



Tig. 24.— White fibrous 
cartilage. 



CARTILAGE AND CONNECTIVE TISSUE 



37 



tion between cartilage and ordinary connective tissue 
is not satisfactory. The difference is due to the fact that 
the fibers are much more loosely woven together in con- 
nective tissue than in cartilage; then, too, there is a marked 
difference in the shape of the inclosed cells. When the 
smooth cells are tightly packed in the inclosing fibers, the 
tissue is called cartilage; when the irregular cells are 
loosely arranged among the fibers, the tissue is known as 
connective tissue. In many cases one is found to grade 
imperceptibly into the other, and what is called cartilage 
by one person might be called connective tissue by another. 

Kinds of Connective Tis- 
sue. — When connective tissue 
is made up of thick, wavy, 
yellow elastic threads, it is 
called yellow elastic tissue. 
It is much like yellow elastic 
cartilage and develops where 
elasticity is desired. It is 
found in the walls of the veins 
and arteries, and scattered 
through the tissue of the lungs. 
White fibrous connective tissue 
is composed of small, white, 
straight inelastic threads. These are bound together in 
such a way as to make the tissue tough and pliable. A 
good representative of this tissue is found in tendons. 

Frequently these yellow elastic and white inelastic fibers 
are woven together into a membrane called areolar tissue; 
this is found highly developed under the skin and holds it 
to .the muscles or subcutaneous tissue. The elasticity of 
areolar tissue may be determined by lifting the skin on the 




Fig-. 25. —Areolar tissue. 



38 PHYSIOLOGY AND HYGIENE 

back of the hand. When an excess of fat is cast into the 
blood, it is carried to the areolar tissue and stored up in 
its meshes as small fat globules, giving rise to the well- 
known adipose tissue. The presence of adipose tissue gives 
the characteristic plumpness to the hands and cheeks of 
children. In old people the excess of fat usually disap- 
pears, the hands become thin, and the cheeks grow hollow. 



CHAPTER VII 

MUSCLES 

Muscles and the Skeleton. — In the discussion on the 
skeleton it was pointed out that, in addition to their use as 
a framework, bones serve the purpose of levers, which, 
under the action of muscles, permit of motion and loco- 
motion. Without muscles, the skeleton would be incapa- 
ble of motion of any kind, and, consequently, movement 
from place to place would be out of the question. 

Motion and Locomotion. — We are so accustomed to the 
many motions of the body that we hardly stop to consider 
how marvelous they are or whence the motive power 
comes. As a result of the contractive power of muscular 
tissue the different parts of the body are capable of move- 
ments that are at once quick, accurate, and graceful. The 
hand is lifted in supplication, the fingers glide rapidly over 
the keys of the piano, or the features take on the many 
characteristic expressions which the face is able to undergo. 

Not only is motion among the different parts of the 
body possible, but by the harmonious action of several 
muscles acting at once the body is able to move from place 
to place, performing its various duties with ease and dis- 
patch. To perform the many functions for which muscu- 
lar tissue is intended over four hundred special muscles 
are developed. In addition to producing motion, these 
muscles help to give shape and beauty to the body, and 
protect the delicate organs from shocks and injuries. 

39 




Fig. 26. — The muscular system (showing important muscles), 
frontalis; b, orbicularis palpebrarum; c, stern o-mastoid ; d, platysma 
myoides; e, deltoid; /, pectoralis major; g, latissimus dorsi; h, triceps; 
i, brachioradialis; j, glutaeus maximus; k, sartorius; I, vastus externus; 
m, tibialis anticus; n, soleus muscle; o, tendo Achillis; p, serratus mag- 
nus; q, biceps; r, rectus abdominalis; s, extensors of toes. 

40 



MUSCLES 



41 



Kinds of Muscles. — The distinction between kinds of 
muscles does not depend so much upon their different sizes 
and shapes as upon the difference in their microscopic 
structure. To know to what class a muscle belongs it is 
necessary to determine something of the size, shape, and 
structure of the fibers of which the muscle is composed. 
Histology teaches us that there are three kinds of muscles : 
striated, unstriated, and cardiac. A comparison of the 
three kinds of fibers which go to make up muscles will 
prove helpful. 

Striated or Voluntary Muscle Fibers. — By far the largest 
number of muscles in the body are striated. If we examine 
one of the muscles of the arm or the 
leg we find that it is composed of a 
large number of small fibers running 
lengthwise with the muscle. A care- 
ful examination shows that these 
fibers are gathered into bundles 
bound together by connective tissue. 
These bundles are called fasciculi 
and are held together by the connec- 
tive tissue which runs in between 
them. This connective tissue also 
spreads out over the entire muscle 
as the perimysium. It is seen, then, 
that the whole muscle is made up of bundles of fibers, or 
fasciculi, and that these fasciculi are composed of many 
small fibers. Since these are the smallest that can be made 
out with the naked eye they are called individual fibers. 
If the individual fiber be boiled, however, and placed under 
the microscope it can be frayed out into numerous minute, 
threadlike structures known as ultimate fibers or fibrillae. 




"Fig. 27. — Striated or vol- 
untary muscle fibers. 



42 



PHYSIOLOGY AND HYGIENE 



Each ultimate fiber is from one inch to two inches long, 
| and about one five-hundredth of an inch in diameter, or 
about as thick as a very small thread of a spider web. 
A fibrilla is divided transversely into tiny rooms called sar- 
comeres, and is covered by a delicate membrane known as 
the sarcolemma. These small cell-like sarcomeres are filled 
with a liquid called hyaloplasm. When an impulse is sent 
through a nerve to an ultimate fiber the hyaloplasm in the 
sarcomeres swells out, causing the fiber to become thicker 
and at the same time shorter. It is the simultaneous short- 
ening and thickening of all the fibrilla? that produce the 
contraction of the whole muscle. These small sarcomeres 
give the striated appearance to vol- 
untary muscles, hence the name. 

Blood capillaries and lymphatics 
closely cover the fibrilla?, conveying 
nourishment to them and carrying 
off waste matter. As already sug- 
gested, minute nerves pass to each 
ultimate fiber, causing it to contract 
at the proper time. From the end 
of each fiber runs a small connec- 
tive-tissue thread, which unites with 
others like it to form the tendon at 
the end of the muscle. 
Unstriated or Involuntary Muscle Fiber. — Unstriated 
muscles are composed of many small spindle-shaped fibers, 
each containing a nucleus at its center. These have no 
cross markings, hence are sometimes called plain muscle 
fibers. An involuntary fiber is about one six-hundredth of 
an inch long, being less in length than an ultimate fiber is 
in diameter. Under favorable conditions an ultimate fiber 




Fig. 28. — Fibrils (show- 
ing- nerve and capillary 
ends). 



MUSCLES 



43 




Tig. 29. — Unstriated 
or involuntary mus- 
cle fibers. 



can be seen with the naked eye, but a plain muscle fiber 
can be detected only by the aid of a good microscope. 

The plain fibers are large at the mid- 
dle, tapering toward the ends. They 
are closely woven into muscular sheets 
or layers, but are not attached to bones 
by means of tendons. They are found 
where a slow regular motion is neces- 
sary, as in the stomach, intestines, 
lungs, and blood vessels. They are 
called involuntary fibers because they 
are not under the control of the will. 

Cardiac Muscle Fibers. — These are 
short, thick, stout muscle fibers, with 
irregular projections at the ends. 
These fit into each other, forming the 
muscular tissue of the heart. The cardiac fibers are like 
the voluntary in that they are striated; they are like the 
plain fibers in that they are nucle- 
ated, involuntary, and not attached 
to bones. Their shape adapts them 
especially for service in the heart, 
where great strength and energy are 
required. 

Special Uses of Muscles. — It is 
needless to say that the function of 
the cardiac muscle is to contract 
and force the blood to the lungs and 
out over the body. The structure of 
the cardiac fibers peculiarly adapts 
the heart to the continued and energetic action which it 
performs. 




"Fig. 30. — Cardiac mus 
cle fibers. 



44 PHYSIOLOGY AND HYGIENE 

The function of the plain muscle is to form sheets, as in 
the diaphragm, to inclose tubes, as in the blood vessels 
and alimentary canal, and to surround openings, as in the 
pyloric and cardiac orifices of the stomach and the pupil of 
the eye. 

The use of the striated muscles, in connection with the 
bones as levers, is to produce the ordinary motions of the 
body as well as locomotion, as in walking, running, jumping, 
etc. In some cases muscles are made up of both striated and 
unstriated muscle fibers, as the muscles of breathing and 
winking. Such muscles are ordinarily involuntary in their 
action, but may be partially controlled by the will, hence 
they are, to a certain extent, voluntary. This double func- 
tion is explained by the presence of the two kinds of fibers. 

Forms of Muscles. — To perform their special functions, 
muscles take on a variety of shapes. However, they are 
usually classed under a few representative forms. A typi- 
cal muscle has an enlarged middle portion which tapers at 
each end to a cord of tough, glistening, white fibrous con- 
nective tissue known as the tendon. Where one end of a 
muscle is divided, each part tapering to a tendon, it is 
called a biceps muscle. The best representative of this 
form is found in the upper part of the arm where the two 
tendons are attached to the shoulder. 

The triceps muscle corresponds to the biceps and lies on 
the under side of the arm, ending in three tendons which 
are attached to the shoulder. A digastric muscle is one 
having two enlargements with a tendon between them. 
The superior oblique muscle of the eye is digastric, its mid- 
dle tendon passing through a pulley, causing the eye to 
rotate. A polygastric muscle is one having three or more 
enlargements. 



MUSCLES 45 

Frequently the muscle fibers run obliquely from a tendon 
passing along the side of the muscle; in such an arrangement 
the muscle is pinniform. Should the fibers run obliquely 
from both sides of a tendon passing along the muscle it is 
called bipinniform. When the fibers are arranged circu- 
larly about an orifice the muscle is known as a sphincter 
muscle; such are found around the mouth, the eye, and at 
various places in the alimentary canal. A highly special- 
ized form of this kind in the pylorus of the stomach is 
called the sphincter muscle. 

Arrangement of Muscles. — Since the 
primary function of muscles is to contract 
and produce motion, they are arranged in 
such a way as to per- 




form this function in 
the most effective 
manner. Where a 
large mass of muscular 

tissue would make the Fig-. 31. — The biceps muscle of the arm. 

part awkward and un- 
wieldy, the muscles occur in thin, broad sheets. Examples 
of these sheets appear around the cranium and across the 
neck and shoulder. When great strength and energy are 
to be secured, the muscles develop into heavy bands or 
cords. 

Very often several muscles are gathered into a conven- 
ient group in which they glide over and among each other 
without friction. In fact, the mechanical arrangement of 
muscles is one of the marvels of the human body. The 
mind wills to move a given part, an impulse sweeps along 
the proper nerve, and out of a large number of muscles a 
certain one contracts, producing the desired motion. 



46 



PHYSIOLOGY AND HYGIENE 



W 



In many cases the muscles are arranged in pairs, one 
acting in opposition to the other, as do the flexors and ex- 
tensors of the forearm; the former, 
by contracting, bend the fingers; 
the latter, contracting in turn, ex- 
tend or straighten the fingers. In 
some cases several muscles are at- 
tached to one bone, which responds 
successively to the action of the 
different muscles. By the harmo- 
nious action of the muscles of the 
different parts of the body the in- 
tricate but graceful motions already 
mentioned are produced. 

Attachment of Muscles. — Mus- 
cles are attached to the various 
parts in different ways. The point 
of attachment which is the least 
movable is called the origin, the 
more movable point is the inser- 
tion. These points, however, may 
be interchangeable. Frequently 
one end of the muscle is free, as in 
the tongue and the muscles of the 
face. Where a muscle does not end 
in a tendon its fibers are attached 
directly to the periosteum of the 
bone. 

Tendons or Sinews. — It was 
stated under the discussion of connective tissue that ten- 
dons are composed of inelastic white fibrous connective 
tissue. They are the strongest tissues of the body, being 



Fig. 32. — Diagram show- 
ing- the action of antag- 
onistic muscles which 
keep the body erect (af- 
ter Huxley). 

a, b, c, d, keep the bod}- from 
falling backward; e,f,g,h, 
keep the body from fall- 
ing forward. 



MUSCLES 47 

able to support a greater strain than either bone or muscle. 
On account of their great strength they are often referred 
to as sinews. 

It would be inconvenient and cumbersome to have mus- 
cles crossing joints for attachment to distant bones. To 
secure convenience and gracefulness of the part, the large, 
soft muscle gives way at the joint to the small, smooth, 
tough tendon, which is attached to the periosteum of the 
bone to be moved. 

For convenience of direction tendons sometimes connect 
the different parts of digastric and polygastric muscles. 
Occasionally mineral matter is deposited in tendons, mak- 
ing them hard and bonelike. Sesamoid bones are merely 
calcified portions of tendons. One of the largest tendons 
of the body is the tendon of Achilles in the heel. 

Composition of Muscles. — In its relaxed condition mus- 
cle is soft and yielding in its structure, having a character- 
istic reddish appearance. It is composed largely of water, 
containing about seventy-five per cent, of that substance. 
In addition it contains considerable quantities of sugar 
and muscle albumen called myosin. The latter is the 
real nutritive part of all cooked lean meats. There are 
also small quantities of mineral matter and traces of hemo- 
globin, an albuminous substance containing iron, which 
will be discussed further under the subject of the blood. 

Strength of Muscle. — The lifting or pulling force of mus- 
cle is very great, but varies considerably in different indi- 
viduals and in different muscles of the same person. A 
peculiar thing about a muscle is that its strength depends 
not only upon its food supply but also upon use and prac- 
tice. A muscle which does not work will in time become 
flabby and may finally disappear altogether. 



48 PHYSIOLOGY AND HYGIENE 

For muscles of ordinary development the lifting power 
has been quite accurately determined. Under the stimulus 
of the will a square inch of the average human muscle may 
be made to lift seventy-five pounds. Let each student 
estimate the diameter of his biceps, and from that calcu- 
late the area of its cross section and finally the full lifting 
power of this muscle. 

Length of Muscles. — The length of muscles is variable. 
The larger number are from three to ten inches long. The 
longest are found in the lower limbs while the shortest ap- 
pear in the face and head. The longest muscle in the body 
is the sartorius, a strap-shaped muscle about eighteen 
inches long, lying to the front and inner side of the thigh; 
its function is to help cross the knees. The shortest mus- 
cle is the stapedius, a small muscle in the ear about one 
sixth of an inch long. 

Immediate Effects of Contraction of Muscles. — The con- 
traction of a muscle is accompanied by a chemical change 
in the muscle substance, and a rise in temperature of the 
muscle itself. As the muscle acts, oxygen is used up and 
the waste product, carbon dioxide, is liberated. Finally 
the muscle experiences fatigue which can only be relieved 
by a rebuilding of the muscle fibers. 

Some Important Muscles. — It can hardly be said that 
one muscle is more important than another, inasmuch as 
the perfect action of the whole body depends upon the 
proper action of every muscle regardless of its size or func- 
tion. Each muscle has its own important place in the 
complete muscular mechanism. However, on account of 
their peculiar location or great size, some of the muscles 
should be discussed in this connection. 

Muscles of the Head. — One of the largest muscles of the 



MUSCLES 49 

head is the occipito-frontalis, a broad, sheetlike muscle 
that extends from the base of the occipital bone over the 
scalp to the frontal bone in the forehead. Two interesting 
muscles are the sphincters of the eyes and the mouth. 
The one surrounding the eye, and which, upon contracting, 
assists in closing that organ, is called the orbicularis pal- 
pebrarum. The one that surrounds the .mouth, and by 
contracting aids in whistling and blowing, is known as the 
orbicularis oris. The muscle that forms the back part of 
the cheek, the fibers of which lie vertically, is the mas- 
set er, a strong muscle attached to the jaws, which aids 
in chewing. 

Muscles of the Arms. — The deltoid is the muscle that 
caps the shoulder and raises the arm from the side to a 
horizontal position. The biceps and triceps lie in the front 
and the back part of the arm, respectively, and, acting in 
opposition to each other, bend and straighten the arm. 
On the side of the forearm next to the palm of the hand 
lie the flexors of the fingers. The extensors of the same 
organs lie on the opposite side of the forearm. These mus- 
cles acting in opposition bend and straighten the fingers. 

Muscles of the Trunk. — Extending from the side of the 
neck across the back of the shoulder is a broad muscle 
called the trapezius, which raises the shoulder and pulls it 
back. Farther down the back another broad muscle 
extends across the ribs under the arms, known as the 
latissimus clorsi; it moves the ribs and assists the process 
of respiration. 

Beginning in the region of the sternum, a large fan- 
shaped muscle extends to the arm, close to the shoulder; 
this is the pectoralis major — a muscle that draws the 
extended arm inward. The rectus abdominis is a thin 



50 PHYSIOLOGY AND HYGIENE 

sheet of muscle which covers the front wall of the abdo- 
men, and which, upon contracting, makes this wall hard 
and tense. 

Muscles of the Leg. — The massive muscle lying in the 
back part of the hip is the gluteus maximus, and is used 
to throw the thigh backward and outward. Farther down, 
and forming the outer part of the thigh, is a large muscle 
called the vastus externus, which assists in extending the 
leg. At about the same height in the front of the thigh is 
a muscle similar to the vastus externus in size and shape, 
known as the rectus femoris, whose function it is to raise 
and extend the leg. 

Beginning at the hip and crossing the front of the thigh 
to the inner side of the knee is a long, straplike muscle 
called the sartorius, the use of which is to bend the leg 
and cross the knees. In the fleshy part of the calf of the 
leg to the back is the gastrocnemius, which assists in 
extending the foot. The lower part of the calf is made 
up of the flexors and extensors of the foot, arranged much 
like the flexors and extensors of the hand. 

Footnote. — A curious arrangement of a muscle is shown in con- 
nection with the eye. A muscle extends forward over the eye, and 
at the front of the socket passes through a small loop of tendon. 
From this point it runs back again and is attached to the eyeball. 
This clever arrangement permits of a freer movement of the ball. 
The loop serves the purpose of a small pulley while the muscle acts 
as a rope. 



CHAPTER VIII 

HYGIENE OF MUSCLES 

Perfect Muscular Development Important. — There was a 
time in the history of Greece when the physical being was 
developed to the highest degree possible. The young men 
were first driven to this development in order that they 
might defend themselves against the raids of hostile races. 
The young women, too, following the example of their 
brothers, gave special attention to athletic training. 

As a result of this care in muscular exercise and devel- 
opment there sprang up a nation representing the highest 
type of form and figure. Young athletes performed feats in 
games and contests that have not been equaled since. Later, 
appreciating the lack of culture and refinement in their 
midst, the people placed a ban on physical training and 
emphasized the development of the mind. Such an idea 
gave rise to many brilliant intellects and great scholars, 
but the lack of physical training was responsible for weak 
bodies and unsightly figures. 

It has only been in recent years that the people have 
discovered that a perfect system of education must provide 
for the symmetrical development of both mind and body. 
To-day not only our normal schools, colleges, and univer- 
sities but also our public schools are making provision for 
gymnastic exercises and physical culture, to the end that 
strong, healthy bodies may do the commands of vigorous 
trained intellects. 

51 



52 PHYSIOLOGY AND HYGIENE 

Why We Need Exercise. — It is almost needless to say that 
exercise is necessary for the proper digestion and assimila- 
tion of the food that we eat. Without complete digestion 
and proper assimilation one cannot enjoy perfect health, 
and without perfect health life fails of the happiness and 
pleasure which a wise Creator intended should be ours. 
But there is more to be desired than mere health. The 
body is a great machine made up of many parts, each 
having its own work to do. If any part grows weak and 
fails to do its work, perfect action of the whole machine 
is impossible. 

It has already been stated that the muscular system is 
composed of about four hundred distinct muscles. That 
these four hundred muscles may be able to work harmo- 
niously and effectively it is necessary that each one be kept 
in the best possible order. Experience has shown that one 
,can bring his muscles to their fullest development only 
by taking proper and sufficient food and exercise. 

Kinds of Exercise. — The kind of exercise that one 
should take depends largely upon the work he does or the 
labor he performs. The farmer, laboring in the field all 
day, finds that he has a sufficient amount of exercise in his 
regular work to meet all demands along this line. The 
section man Who toils all day through in working the rail- 
road bed, hardly needs any special exercise to develop his 
muscle. The schoolboy on the farm usually has enough 
chores to do morning and evening to give his muscular 
system full development. 

Ordinarily, the person who is engaged in outdoor pur- 
suits a part or all of the day will need no suggestions to 
assist him in the proper training of his body. It is the 
boy and the girl, the man and the woman, who are kept 



HYGIENE OF MUSCLES 53 

indoors from day to day, who must take regular and system- 
atic exercise if they wish to enjoy good health and possess 
a well-proportioned, vigorous, comely body. A few general 
suggestions concerning exercise may be helpful in this con- 
nection. 1 

Exercise for Children. — It has already been suggested 
that most of the boys on the farm get all the exercise they 
need in doing the necessary work about the home. The 
same may be said of the girls on the farm. However, in 
our towns and cities some attention must be given to the 
matter of exercise. In some of our great cities in certain 
quarters, the boys and girls are so shut in by the streets 
and large buildings that they are deprived of the exercise 
that strong, healthy boys and girls usually take on their 
own account. 

Even in some of our smaller towns the children (Jo not 
have space at home or at school for play, and, having no 
regular work to do, they grow fretful and languid and are 
sometimes forced to take up questionable amusements. If 
possible, homes should be built on lots sufficiently large to 
permit of those sports and games so dear to the heart of 
every boy and girl. School grounds in both city and 
country should be laid out with an eye not only to beauty 
but to utility with respect to exercise for the children dur- 
ing intermission. Here the old-fashioned games of " Black 
Man," "Hide and Seek," "Dare Base," "Ball," and many 
others can - be played, providing the boys and girls with 
both entertainment and muscular development. » 

The parent or teacher who is wise enough to permit, 

1 The most of us should take some exercise for the sake of develop- 
ment, and it should be such as will call into use muscles doing the 
least work in our daily occupations.. 



54 PHYSIOLOGY AND HYGIENE 

and even to encourage, this form of sport will be repaid a 
hundred-fold by seeing the color come to the cheek, the 
luster to the eye, and the muscles grow into symmetrical 
rounded cords of active tissue. Let it be remembered that, 
while the child is young and in the growing period, the 
lymphatic system is filled with waste matter from broken- 
down tissue, and it is necessary that it take exercise enough 
to move the sluggish stream of lymph along in order that 
the waste material may finally be cast from the system, 
leaving the body in an active healthy condition. 

It is a well-known fact that both mind and body grow 
strong by continued use. Let us keep in mind the neces- 
sity, then, of providing the children with those exercises 
which will develop all the muscles of the body, so that 
they may possess bodies vigorous and active for the duties 
which they are later to perform. 

Exercise for Young People. — It is an encouraging sign 
of the times that something definite is being done these 
years in our schools and colleges in the matter of physical 
training. The fact that our school sports are frequently 
conducted in an improper manner does not argue that this 
new movement is not in the right direction. The day has 
gone by when mental training at the expense of physical 
development is to be justified in any well-regulated system 
of education. " A sane mind in a sound body " is the de- 
sire of every student of intellectual progress. 

The development of brain fiber goes hand in hand with 
the development of muscular fiber. In truth, the healthy 
growth of the former depends largely upon the regular and 
complete development of the latter. 

Under wise and careful supervision, then, our young peo- 
ple should be led through' such a course of athletics that 



HYGIENE OF MUSCLES 55 

every cell and fiber and tissue in the body will respond to 
the call of the brain for support in performing its functions. 
For an hour each evening the boys and girls should gather 
on the field for the purpose of exercise and recreation. 

For the boys no sport excels our great national game 
of baseball, while for the girls the exercise provided by 
basket ball or tennis will prove beneficial. In fact, the 
latter games are adapted to the demands of the young 
people of both sexes. 

Football, if played under the proper rules and regula- 
tions, develops to the fullest extent the muscles of the 
body and the faculties of the mind. If but few restric- 
tions are placed upon the game, however, football tends 
to brutality and dishonesty. Under the inspiration of the 
applause from enthusiastic followers, young men are im- 
pelled to do those things of which they would be ashamed 
under other circumstances. Recent changes in the rules 
promise much for the success of this much-discussed yet 
popular game. 

Golf, while not so exciting as some of the other sports, 
furnishes suitable exercise for those who enjoy hill climb- 
ing and the exhilarating effects of outdoor life. Many of 
the old-fashioned games that take the young people over 
the prairies, the hills, and through the woods with a rush 
are exciting and invigorating. Skating, where the ice is 
sufficiently thick and plentiful, furnishes sport and exer- 
cise that can hardly be duplicated in any other form. 
Bicycling provides a pleasant diversion for those who own 
wheels. 

TTalking parties and outing clubs, organized for the pur- 
pose, of exploring local objects of interest, are happy means 
of instruction and exercise. Swimming is a sport that 



56 PHYSIOLOGY AND HYGIENE 

should be indulged in by both boys and girls. In addition 
to its value as an exercise it is an accomplishment that 
may be the means of saving a life at some critical moment. 

Where these outdoor sports are impossible, regular gym- 
nasium work furnishes the best substitute for exercise. 
Drills with wands, dumb-bells, and Indian clubs are inter- 
esting and furnish the means of systematic muscular devel- 
opment. It should be borne in mind that those sports 
and games are best that are most thoroughly enjoyed by 
the participants. 

As the result of definite effort now being made along 
the line of physical training it is to be hoped and expected 
that the future will see fewer languid, listless pupils and 
students in our schoolrooms. Moreover, the next genera- 
tion should be made up of men and women strong, straight, 
and muscular, comely in appearance, and healthy in mind 
and body. 

Exercise for Older People. — During the growing period 
of life it is necessary that exercise should be abundant and 
vigorous in order that respiration and circulation be kept 
active, thus providing for a sufficient supply of oxygen 
and the rapid and complete elimination of waste matter. 

When this growing period is past, however, and fewer 
changes take place in the various tissues of the body, milder 
forms of exercise may be substituted for those of earlier 
life. Walking, more or less active, will prove beneficial to 
people of all ages who are able to get out of doors. Hunt- 
ing, if indulged in to a moderate degree, is a suitable exer- 
cise for men who have the power of endurance. • Horse- 
back riding is a good, old-fashioned exercise that seems to 
be losing ground, but which has a value peculiar to itself. 

Driving is a pastime, however, that holds its favor with 



HYGIENE OF MUSCLES 57 

all classes of people, and is a splendid exercise for older 
folks who are unable to take any of the more active 
forms. Aged people who reside close to electric lines find 
a delightful exercise in car rides to city parks and country 
pleasure resorts. Automobile riding is a fascinating diver- 
sion that is bound to increase in popularity as the cost 
of machines decreases and the management of them be- 
comes easier. In every case the particular kind of exercise 
must be determined by the age, health, and activity of the 
individual. 

Care in Taking Exercise. — Persons of mature age will 
hardly need any suggestions concerning care in the matter 
of exercise. Young people, however, may not find a word 
of caution amiss. In the midst of many of our most popu- 
lar sports the young man or young woman may forget the 
real object of exercise and, mindful only of the outcome 
of the game, exert himself or herself beyond the point of 
endurance. 

Many a young man has strained a muscle or broken 
a leg in a final great effort to win a game of football or 
make a spectacular play at a critical stage in the prog- 
ress of the game. Young women often fall down from 
sheer exhaustion as a result of continued and violent exer- 
tion on the basket-ball ground. 

Not infrequently in our school " meets" boys enter con- 
tests in walking and running and, impelled by school pride 
and goaded on by hundreds of their school fellows, walk 
or run until their weary limbs fairly give way and they 
fall completely exhausted at the side of the track. In con- 
tests in the gymnasium, where rivalry is keen and intense, 
foolhardy students often go beyond the bounds of reason 
and in their efforts to win, fall and strike the hard floor, 



58 PHYSIOLOGY AND HYGIENE 

shocking the brain or some other vital part, bruising the 
muscles, or seriously and permanently injuring the neck 
or backbone. 

Young people should be taught moderation in the matter 
of games and sports of all kinds. Boys and girls who are 
especially weak in any part of the body, or who are liable 
to suffer in any way from the excitement common to 
most cf our games, should never take part in these 
exercises. 

Diseases of Muscles. — It is a fortunate thing indeed 
that muscles are not subject to the ravages of many dis- 
eases. Several tissues of the body of less importance than 
the muscles are preyed upon by diseases of many kinds. 
It is of interest to note in this connection, however, some 
conditions that affect the muscles directly or indirectly. 

Tetanus. — It has been shown how a muscle is made to 
contract as the result of a nervous impulse sent out over the 
branches of a nerve to the different fibers of the muscle. 
The impulse may last but an instant, producing a momen- 
tary effect on the muscle, or a large number of impulses may 
be made to follow each other so rapidly that the muscle is 
kept in a continuous state of contraction. The term teta- 
nus is used to designate a diseased condition of the body in 
which the muscles of a part or all of the body are held in a 
more or less violent and rigid spasm caused by a continued 
abnormal application of impulses. These spasms are caused 
by a sudden change of temperature or by a wound result- 
ing from the cut of an old knife, the puncture of a rusty 
nail, or any other violent irritation of nerves poisoned 'by 
toxin from tetanus bacteria. In this disease the mus- 
cles become so rigid and tense that they may be torn from 
their attachments before they will relax. This disease has 



HYGIENE OF MUSCLES 59 

been known to affect domestic animals in much the same 
way as it does man; in fact, it in every case is due to the 
same cause. 

Lockjaw. — A well-known form of tetanus is called lock- 
jaw. This disease arises from amputation, from the tear of 
a blunt instrument, or laceration produced in any other 
way. It is almost invariably preceded by wounds or inju- 
ries of some kind. Often a defective tooth produces a 
nervous condition that brings on lockjaw. 

In the earlier stages of the disease the muscles of the 
jaws and neck begin to contract. Later, those of the throat 
and breast are affected, and often the contractions spread 
to the muscles of the whole body. The jaws slowly close 
or, less frequentfy, come together with a snap and are held 
under such tension that they cannot be pried open. An 
intense pain develops under the sternum and shoots through 
the trunk. 

In very severe cases the great muscles of the back con- 
tract, drawing the head back until the rigid body rests 
upon the heels and head. Sometimes the muscles of the 
front part of the body contract, bringing the knees up to 
the face in a very painful position. 

Many remedies have been tried, but practically all have 
failed. The best method of treatment is to keep the 
patient quiet and assist him in maintaining his strength. 
Care should be taken to see that nothing be permitted to 
irritate the nervous system of the individual, as irritation 
only tends to aggravate the conditions. In spite of every- 
thing that can be done the majority of cases of lock- 
jaw prove fatal, which marks it as the most dreadful form 
of tetanus. 

Hydrophobia. — As is the disease tetanus, so is this a 



60 PHYSIOLOGY AND HYGIENE 

nervous rather than a muscular disease, but since it affects 
the muscles in a peculiar way it is treated in this connection. 
Hydrophobia is an acute infectious disease, caused by the 
virus in the secretions from the mouth of a mad dog get- 
ting into a wound of the skin. Usually the virus is intro- 
duced into the wound made by the bite of the dog itself, 
and the symptoms of the disease develop sometimes within 
a couple of weeks, the development extending frequently 
through several months or even a year. 

When the disease is about to manifest itself the wound, 
which has perhaps healed over, becomes inflamed or irri- 
tated and the individual grows despondent, restless, and 
exhibits a kind of indefinite fear. Later the patient be- 
comes talkative, yet manifesting a certain gloomy, mel- 
ancholy disposition. These conditions gradually lead up to 
the final stage of excitement and tetanic spasms. 

The patient grows extremely thirsty, yet when water or 
other liquid is taken into the mouth he cannot drink it; 
the muscles of the throat, neck, and breast become con- 
vulsed, leaving the sufferer weak and exhausted, yet with 
a still greater desire for drink than ever. Terrified and 
distressed, he repeats the efforts to allay his thirst, only to 
be thrown into more severe convulsions than before. 

The very thought of a liquid or the sound of running 
water throws him into violent spasms that often extend 
to the muscles of the whole body. These periods of vio- 
lence gradually die away, only to recur at frequent in- 
tervals. This stage extends through a period of from 
three to five days or until death comes from choking or 
from sheer exhaustion. In the latter case the convulsions 
cease and often the power of swallowing returns before 
death. 



HYGIENE OF MUSCLES 61 

Pasteurism for Hydrophobia. — Although many reme- 
dies were tried from time to time, none were found of value 
until about 1885, when Mr. Pasteur, a French bacteriologist, 
proved that hydrophobia could be successfully treated by 
injecting into the blood of the individual virus from the 
spinal cord of a rabbit that had died of rabies. 

His method was to begin the injection as soon as it was 
shown definitely that the bite was that of a rabid dog. 
He first injected a very weak form of the virus into the 
system by means of a hypodermic syringe. Daily, for 
thirteen days, he increased the strength of the poison until 
the system of the patient could stand fresh, strong virus. 
His theory was that the poison from the rabbit neutralized 
the effect of that of the mad dog and prevented the de- 
velopment of hydrophobia. His method has been widely 
adopted and many cases have been successfully treated by 
means of his remedy. So many, in fact, that Pasteur In- 
stitutes have been established throughout the civilized world. 
To-day instead of being a source of danger, and hopeless 
sorrow to his friends, the hydrophobia patient may be hurried 
to an institute where a speedy cure is highly probable. 

Madstones. — There has long been a popular notion that 
a land of stone picked up in different localities, or a certain 
spongy substance taken from the stomach of a cow or a 
deer, will, when applied to the wound made by the bite of 
the mad dog, adhere till all the poison has been absorbed, 
and that it will then drop off. Although many cases of al- 
leged cures by madstones are on record it is well to bear in 
mind that while delaying to apply the madstone the life of 
the patient is further jeopardized because the disease may 
progress beyond the possibility of a cure by the "Pasteur 
Treatment." 



62 PHYSIOLOGY AND HYGIENE 

Rabid Dogs. — Hydrophobia is a dreaded disease on ac- 
count of its peculiar effect upon the patient and the large 
per cent, of fatalities that follow it. For this reason every- 
one should know something concerning its symptoms in 
dogs and other animals. 

During its earliest stages of development the dog usually 
changes its manner and actions. It loses its appetite, be- 
comes restless, frequently changes its position, and slinks 
away at the approach of its master. Later an abnormal 
appetite is developed and the dog rejects its ordinary food 
and eats uncommon articles such as straw, chips, and 
similar objects. 

At this stage the animal shows a fighting disposition 
and goes around snarling and snapping at objects about it, 
both animate and inanimate. It becomes excited and its 
whole nature seems to change. It rushes about frothing at 
the mouth, biting or snapping at every person or animal it 
meets. At this stage there can hardly be any doubt as to 
the nature of the trouble. 

Unless absolutely necessary, the mad animal should not 
be killed, but, if possible, captured and confined until it is 
proved that the disease is or is not rabies; otherwise any- 
one bitten may be kept in great suspense for months, 
waiting for, yet dreading, the development of hydrophobia. 
It may be proved that the suspected dog did not have 
rabies, and if that be the case anyone who was bitten may 
be saved weeks and months of unnecessary anxiety and 
distress. 

Effects of Alcohol on Muscles. — When alcohol is first 
taken into the system it affects the muscles indirectly 
through the nervous system. Having a great affinity for 
water, alcohol extracts it from the nerves, destroying 



HYGIENE OF MUSCLES 63 

their sensitiveness for carrying impulses, and as a result the 
brain loses control over the action of the muscles which are 
supplied by the nerves affected. Consequently, the drinker 
trembles in his actions and staggers in his walk. 

If more alcohol be taken and the nerves be affected still 
further, the individual may lose entire control of himself 
and fall down in a stupor in which all muscular action 
ceases but that which keeps up circulation and respira- 
tion. If no more alcohol be taken, after a while the nerves 
and muscles may return to their usual condition, but if 
the drinking be kept up these organs are at last perma- 
nently affected and staggering becomes characteristic of 
the drinker's walk and he shakes and trembles in all his 
movements. 

Fatty Degeneration. — Another effect, still more serious 
than the first, results from long-continued drinking. In 
the healthy body when cells are broken down they are 
immediately built up from the food material in the blood 
and the tissue is as strong as before. When muscle cells 
are torn down in the presence of alcohol it is impossible for 
them to be built up again. 

Nature, however, provides the material at the proper 
time, and since it cannot be built into muscle cells it is 
deposited in the place of these cells, usually in the form 
of hydrocarbons or fat. Cell by cell the muscular tissue is 
worn away and fatty matter is deposited in its place. After 
some time large portions of muscle have been replaced by 
these fatty deposits and the body becomes fleshy. Appa- 
rently the drinker has grown strong and vigorous, but the 
appearance is deceptive. An examination proves that the 
once strong, solid muscle has given way to a flabby, inac- 
tive tissue that is incapable of contracting with sufficient 



64 PHYSIOLOGY AND HYGIENE 

energy to perform even the commonest kinds of labor. 
Such a condition is known as fatty degeneration. 

Effects of Tobacco on Muscles. — The effect of tobacco 
on muscular tissue is similar to that of alcohol. It tends to 
harden both the nerves and the muscle fibers, destroying 
the quick action and springiness of muscles over the whole 
body. The effect of cigarettes is especially pernicious in the 
case of the growing boy. The narcotic of tobacco does not 
permit of the development of new cells nor the repair of 
the old ones. The stunted growth and weak body of the 
cigarette fiend testify to the evil effects of cigarette smoking 
not only upon the muscular system but upon the entire 
body. 



CHAPTER IX 
ORGANS OF CIRCULATION 

The Importance of the Circulation of the Blood. 1 — The 

discovery of the circulation of the blood was made by 
Harvey about 1628. It seems strange, in the absence of 
any reasonable explanation for many of the ordinary phe- 
nomena of some of the organs of the body, that the circu- 
lation of the blood should not have suggested itself to some 
of the earlier scientists. The food elements are taken 
up by the blood and carried out over the entire body, 
where they are built into the tissues of the same. Return- 
ing, the blood stream conveys waste matter to the central 
organ, from where it is sent to the lungs or skin or kid- 
neys, and eliminated from the body. 

Through practically the whole system the crimson 
stream pours and rushes and whirls. As our large river 
systems ramify almost the entire area of our country, so 
the stream of blood pierces almost every organ and tissue 
and structure, receiving here a particle of food or frag- 

1 Certain of the ancients believed that the blood was sent out from 
the heart to the distant parts of the body, where it was used up in 
nourishing the body. Later scientists put forward other ideas re- 
garding the movement of the blood, but it remained for Harvey, 
an English physiologist, to advance the theory of the circulation of 
the blood in the early part of the seventeenth century. He was 
persecuted for his views; but Malpighi, a noted Italian anatomist, 
a quarter of a century later proved that he was right. Malpighi 
demonstrated beyond doubt the circulation of the blood in the 
frog's foot. 

65 



PHYSIOLOGY AND HYGIENE 



ment of refuse matter, and depositing there the material 
for a living cell or a portion of waste matter to be elimi- 
nated from the body. 

Since the blood is so closely connected with the proc- 
esses of secretion, respiration, absorption, assimilation, ex- 
cretion, etc., it is necessary that we become familiar with 
the organs instrumental in maintaining its circulation as 
well as its composition and uses. 

The Heart. — Lying in the lower part of the thoracic 
cavity, almost enveloped by the two divisions of the lungs, 
is the heart. This is a pear-shaped muscular structure, 

varying from the size of the 
owner's fist to almost twice 
that size, and weighing from 
one half pound in the female 
to three fourths pound in 
the male. 

The base, or larger end, of 
the organ is held securely, 
a little to the right of the 
middle of the body, by the 
lungs and the large blood 
tubes connecting with it. 
The smaller pointed end ex- 
tends downward and to the 
left of the median line. 

Being bound at the upper 
large end and free in the 
lower portion, the heart can 
respond to its contraction only at the latter end, where it 
beats against the front wall of the chest at a point be- 
tween the fifth and sixth ribs. The fact that the heart 




I'ig-. 33. — External view of heart 
showing- large blood vessels. 



ORGANS OF CIRCULATION 67 

can be heard more distinctly on the left side has given 
rise to the popular idea that the larger part of the heart 
lies on the left side of the thorax. This idea, however, is 
hardly correct, as a median line drawn vertically through 
the chest would divide the heart into two almost equal 
parts. 

Membranes of the Heart. — Covering the heart at every 
point but the base is a double-walled serous membrane 
called the pericardium. Between the two layers of the 
pericardium is a liquid secreted by the membrane itself 
called the pericardial fluid. This serves to lubricate the 
inner surface of the pericardium, preventing friction. At 
the base the pericardium closely surrounds the blood ves- 
sels that enter the heart. Lining the inner surface of the 
cavities of the heart is the endocardium, a membrane sim- 
ilar to the pericardium in appearance and structure. 

Cavities of the Heart. — The heart contains four cavities, 
two auricles and two ventricles. These receive the blood 
during the period of relaxation, and serve as reservoirs for 
the same until the contractions of the -heart drive it out 
over the body or to the lungs. On account of the differ- 
ence in their uses the auricles and ventricles differ in size 
and structure. 

The Auricles. — These are small ear-shaped flaps at- 
tached to the upper part, or base, of the heart. Indeed, 
they are so small that, on first sight, they appear as mere 
appendages to this organ. Their walls are thin and, as 
already stated, are composed of the stout cardiac muscle 
fibers. The large descending vena cava and the equally 
large ascending vena cava enter the side of the right auri- 
cle at about the same place, conveying the impure blood 
from all over the body into this cavity. 



68 



PHYSIOLOGY AND HYGIENE 



At the proper time the blood which has collected in 
the right auricle drops into the right ventricle. The left 
auricle receives the blood from the three or four pul- 
monary veins and discharges it into the left ventricle. 
The blood leaves both auricles at the same time. 

The auricles are merely reservoirs, and inasmuch as they 
contract but slightly and suffer little strain, their walls 
are thin and rather weak. 

The Ventricles. — In addition to their use as reservoirs, 
the ventricles perform the function of an engine, con- 
tracting with great energy and forcing the blood to dis- 
tant parts of the body. For this reason their walls are 
much thicker than those of the auricles. In fact, the ven- 
tricles make up the greater portion of the heart, not so 
much because their cavities are larger than those of the 

auricles as that their walls 
are vastly thicker. 

Since the left ventricle 
drives the blood to the head 
and extremities of the limbs, 
and the right ventricle forces 
it only to the lungs, which lie 
around the heart, the walls 
of the former are correspond- 
ingly thicker than those of 
the latter. 

If a heart be cut trans- 
versely, the ventricles appear 
not as real cavities but as 
mere slits in the muscular tis- 




Tig. 34. — Diagram showing- course 
of the blood through the heart. 



sue. The right ventricle receives the blood from the right 
auricle and discharges it through the pulmonary artery. 



ORGANS OF CIRCULATION 



69 



The blood from the left auricle falls into the left ventricle 
and is forced out through the aorta. 

Valves and Their Attachments. — It has just been sug- 
gested that there is an opening between the right auricle 
and right ventricle, and another 
between the left auricle and left 
ventricle. It might be stated here 
that there is no opening between 
the right and left sides of the heart. 

After the blood has been dis- 
charged from the ventricles and 
their walls relax, it is easy to see 
how the blood falls into these lower 
cavities. It may not be so easy to 
see why the blood is not driven 
back into the auricles when the 
ventricles are filled and their walls 
once more contract. To prevent 
such an action small membranous 
flaps are developed in the openings 
between the two cavities. When 
the ventricles become filled from 
above, the blood floats these flaps 
out and up until they complete- 
ly fill the openings, thus prevent- 
ing the flow of the blood back 
into the auricles when the walls 
of the ventricles contract. Since 
the blood cannot return to the auricles, it is forced out 
through the connecting tubes. 

It might be suspected that the great pressure of the 
blood from below would push these flaps on through the 




Fig. 35. — The heart. 

a, right pulmonary vein cut 
short; b, cavity of left au- 
ricle; c, thick wall of left 
ventricle; d, portion of the 
same with papillary muscle 
attached; e, papillary mus- 
cles; /, the segments of the 
mitral valve; g, aorta; h, 
pulmonary artery; i, semi- 
lunar valves; /, aorta and 
its branches. 



70 PHYSIOLOGY AND HYGIENE 

openings, permitting the blood to flow once more into the 
auricles. This indeed would be the case were it not for the 
fact that the flaps are held back by small threads of 
inelastic tissue, which permit them to rise only until they 
come together, completely closing the orifices. At this 
point they are held down firmly against the upward pres- 
sure of the blood by the tendinous threads. 

These cords are not attached directly to the walls of 
the heart, since, when the latter contracts, its length de- 
creases. This shortening of the heart would slacken the 
threads, permitting the flaps to be pushed up into the 
auricles. To prevent this last action, the threads are 
attached to the top of small eminences or pillars of mus- 
cles that project from the walls. As the heart decreases 
in length in one direction, these pillars contract and de- 
crease in length in the other direction, and, pulling on the 
threads, prevent the slackening of the same. On account of 
their structure these threads or cords are called chordae 
tenclinse, and the muscular projections, papillary muscles. 

The arrangement just described provides a very effect- 
ual check valve to prevent the backward flow of the blood 
into the auricles. Since there are three of these flaps be- 
tween the right auricle and right ventricle, the combination 
is called the tricuspid valve. The combination of the two 
flaps between the left auricle and left ventricle is called 
the bicuspid or mitral valve. At the orifices of the aorta 
and pulmonary arteries are three folds of connective tissue 
which swell out and close the opening at the end of the 
ventricular contraction, preventing the return of the blood 
to the ventricles. These are the semilunar valves. 

Nerves of the Heart. — The action of most of the 
muscular organs of the body is controlled by the will and 



ORGANS OF CIRCULATION 71 

consequently they have no regularity of motion. Even 
the involuntary muscles of many of the vital organs are 
slow and irregular in their motions. In the heart, how- 
ever, we have a muscle whose action is surprisingly even 
and regular. Day after day and year after year it pounds 
energetically along, performing its life-giving function with 
but a brief period of relaxation and rest at the close of 
each beat. Once every second it sends a crimson flood 
swirling out into every nook and crevice of the tissues. 

One cannot help but wonder what it is that controls the 
regular throbbing and beating of this wonderful organ. It 
is a well-known fact that certain emotions of the mind, as 
anger and fear, increase the intensity of the heart's throb. 
The effect of the state of mind on the beat of the heart 
led the ancients to believe that the heart is the seat of all 
the emotions. It remained for modern science to prove 
that this old idea was wrong, and to prove further that the 
beat of the heart is controlled by certain nerve ganglia that 
lie in the inner walls of the heart itself. These ganglia are 
found in two groups, one of which is located in the base 
and the other toward the apex of the heart. The first gan- 
glia are called the ganglia of Remak, and the second, the 
ganglia of Bidder. The action of these nerve masses is to 
a certain extent affected by a branch of the pneumogastric 
nerve, giving rise to the emotional effect mentioned above. 

The Beat of the Heart. — It is a popular notion that the 
heart beats all over at the same time, and that it labors on 
until death, with no intervals of rest or relaxation. The 
fact is that the fibers of the heart work less than half of 
the time. The heart beat includes two periods, a period 
of contraction, called the systole, and a period of relaxation, 
known as the diastole. 



72 PHYSIOLOGY AND HYGIENE 

How the Heart Contracts. — - The contraction of the heart 
consists of two parts, the systole of the auricles and the 
systole of the ventricles. At the close of a period of relax- 
ation the fibers in the base of the heart begin to contract, 
diminishing the capacity of the auricles. The contraction 
sweeps downward from the auricles across the ventricles, 
passing out at the apex of the heart. By the time the 
fibers in the walls of the ventricles begin to contract those 
of the auricles have relaxed and remain in that condition, 
while the contraction moves across the ventricles. 

The whole period of contraction, or the systole, occu- 
pies only about two fifths of the entire heart beat, and 
yet neither the auricles nor ventricles contract all of this 
time. Thus it will be seen that the heart as a whole is 
actually working less than one half of the time and the 
auricles only a very small fraction of the whole time. 
After the impulse passes out from the apex both auricles 
and ventricles remain at rest during the remainder of the 
beat or during the diastole, when a new contraction com- 
mences at the base, continuing across the heart as before. 

Number of Heart Beats. — The rate at which the heart 
beats varies in different individuals and at different ages. 
In infants it is especially high, running sometimes up to 125 
or 130 per minute. In the mature individual, however, 
the rate averages about 72, being slightly higher for women. 

Some diseases increase the number of heart beats, espe- 
cially if the action of the heart is not perfect. In the case 
of strong healthy hearts, disease does not affect the rate so 
much. Certain drugs and medicines have a tendency to 
increase the number of beats, while others have the oppo- 
site effect. Excessive labor or exercise usually increases 
the number of beats. The rate at which the heart con- 



ORGANS OF CIRCULATION To 

tracts is often an indication of the condition or health of 
the body. In old age the number of beats falls as low as 
60 or 65. 1 

The Sound of the Heart. — When the ear is placed on 
the chest wall over the heart, the beat appears to be made 
up of two distinct parts. The first is caused by the con- 
traction and the second by the relaxation of the fibers of 
the heart. In addition to these two predominating sounds 
may be heard others of less intensity that are produced by 
the sudden closing of the valves. 

Physicians have made such a study of the sounds com- 
posing the heart's beat that they can usually determine 
by placing the ear over this organ whether it is perfect or 
diseased. The slightest variation from the normal beat 
suggests the location and nature of the defect of the organ. 
The many disorders to which the heart is subject have 
been studied by the physician by means of the ear alone 
or the aid of a specially constructed instrument called 
the stethoscope. As a result of this study many cases of 
heart disease have been successfully treated that might 
otherwise have proved fatal. 

x The effect of the heart's beat may be felt by placing the finger on 
the wrist or the temple. The throb felt at these places is called the 
pulse, 



CHAPTER X 

THE BLOOD VESSELS 

Blood Tubes or Vessels. — In hot-water heating systems 
the water is heated at some central point, and is permitted 
to flow out through a set of pipes, whence, after being 
cooled, it returns through another set of pipes to the heat- 
ing apparatus. Residences and other buildings in large 
cities are supplied with water conveyed through pipes con- 
nected with a large reservoir. After the water is used for 
bathing and washing it is collected by another set of pipes 
which unite to form a sewerage system, by means of 
which it is carried out of the city. 

We sometimes speak of the water in the heating sys- 
tem and in the waterworks as circulating. In the human 
body we, have a real system of circulation, inasmuch as 
the blood is sent from the central organ, the heart, and 
after bathing the distant tissues of the body is returned to 
the heart whence it was propelled. It is interesting to 
notice here that, while the blood is sent out through one 
set of tubes called the arteries, it is returned as blood 
through the veins or as lymph through the lymphatics. 
A description of these different kinds of tubes is necessary 
to be able to understand the matter of circulation fully. 

The Arteries. — The ancients applied the term arteries to 
these tubes because after death they contained no blood, 
but were found filled with air. It was thought that they 
were connected with the windpipe, from which they 

74 



THE BLOOD VESSELS 



/.) 




Fig. 36. — Struc- 
ture of an ar- 
tery. 



received their supply of air. Later it was discovered that 

the arteries in the living body convey the blood from the 

heart to all parts of the body, dividing and 

subdividing into smaller ramifications, which 

finally terminate in capillaries. 

As the arteries increase in number' they 

decrease in size, varying from a little less 

than one half an inch in diameter in the 

aorta to a tube so small that it can be seen 

only by the aid of a microscope. Over 

three hundred arteries in the human body 

are of sufficient size to receive names. As 

already stated, the aorta and the pulmonary 

artery carry blood from the left ventricle 

and the right ventricle respectively. 

Structure of the Arteries. — Most arteries are composed 
of three layers. The outer coat is made 
up of tough, felted bundles of white fibrous 
connective tissue. Running through the 
fibers are numerous nerves and blood 
vessels. This coat is strong and inelastic. 
The middle coat is a mixture of plain 
muscle and yellow elastic fibers. In the 
thin sheets of muscular tissue the in- 
voluntary fibers are arranged circularly. 
Alternating with these muscle fibers are 
thin layers of yellow elastic fibers running 
through a small lengthwise of the artery, 
ar ery an vein. The inner coat is a thin, smooth, deli- 

A, artery; V, vein. ' . _ 

cate membrane of elastic tissue lined with 
a layer of epithelial cells. The middle coat contains 
elastic fibers to permit of an increase in size of the tube, 




Fig. 37. — Trans- 
verse section 



76 



PHYSIOLOGY AND HYGIENE 




Fig.38.- 

Structure 
of veins. 

thin and 



it contains muscle fibers which contract and diminish the 
bore of the tube, preventing too rapid a flow of blood. 
The outer coat is made strong and inelastic to prevent too 
great a distention of the vessel with a consequent 
bursting of the artery. 

Veins. — Lying side by side with the arteries 
is another set of blood tubes called veins. These 
tubes are formed from many small veins or 
veinlets which receive the blood from the cap- 
illaries and convey it toward the heart. The 
veins differ from the arteries in both structure 
and use. The walls of the arteries are so thick 
and strong that the tubes remain open even 
after the blood has been removed from them. 
In the case of the veins, however, the walls are 
flabby, permitting the 
tubes to collapse when they become 
empty. 

Structure of the Veins. — The three 
coats mentioned as entering into the 
structure of the arteries are present 
in the walls of the veins. The}?- 
are not all highly developed though. 
The outer, tough, inelastic coat 
gives strength to the tubes. The 
middle coat is much less developed Fig. 39. — Fibrils (show- 
than in the artery, but contains a in * nerve and capillary 
few muscle fibers. The inner coat 

is likewise very much reduced in the veins. In many 
places it is thrown into pocketlike folds, forming the so- 
called valves of the veins, which serve to prevent the 
backward flow of the blood. There are many of these 




THE BLOOD VESSELS 



77 



valves in the veins of the lower limbs, fewer in the veins 
of the upper part of the body, and they are entirely lack- 
ing in the large veins close to the heart. The veins are 
supplied with but few nerves. 

Capillaries. — Connecting the arteries and veins is a net- 
work of very small tubes known as capillaries. These tubes 
are about one fiftieth of an inch long and usually not much 
larger than the blood cells; in many 
cases the latter are larger than the tubes 
and crowd them as they pass through. 

The walls of the capillaries are com- 
posed of a single layer of flattened epithe- 
lial cells, which in reality is a continua- 
tion of the inner layer of the arteries 
and veins. The capillaries receive the 
blood from the arteries and convey it to 
the veins. As the blood passes through 
the capillaries the phenomenon of osmosis 
takes place through the thin walls. More- 
over the white blood corpuscles pass through at the same 
time. 

Important Arteries. — One of the leading arteries in the 
body conveys the impure blood from the right ventricle to 
the lungs and is called the pulmonary artery. The aorta, 
the largest artery in the body, opens out of the left ventri- 
cle upward and makes a graceful turn backward, passing 
clown behind the heart through the diaphragm. Close to 
the semilunar valves it gives off the two coronary arteries 
that nourish the walls of the heart. 

At the beginning of the arch of the aorta arises the 
innominate artery, while a little farther back another 
branch, the left carotid, is given off. Just before it turns 




Fig. 40. — View of 
capillaries. 




Tig. 41.— General plan of the heart and large bloodvessels. 
a, a, aorta; b, descending vena cava; c, ascending vena cava ; d, d, kidneys 
e, jugular vein; /, external jugular vein; g, g, iliac veins; h, h, iliac arteries 
i, carotid artery;;,/, azygos vein; k, cceliac axis; I, hepatic veins; 
m, m, renal veins; n, n, subclavian arteries; o, o, subclavian veins; p, heart ; 
r, r, renal arteries. 



78 



THE BLOOD VESSELS 79 

downward the aorta gives off the left subclavian artery, 
which conveys the blood to the left arm. Soon after leav- 
ing the aorta, the innominate artery divides into the right 
carotid and the right subclavian artery, the latter carrying 
the blood to the right arm. The left and right carotids 
convey the blood to the head. 

Numerous branches are given off by the aorta in its down- 
ward course. As it passes through the chest it is called the 
thoracic aorta, and below the diaphragm it is known as the 
abdominal aorta. Just below the diaphragm is given off a 
group of small arteries forming the coeliac axis. The 
important arteries of this group are the gastric, the splenic, 
the pancreatic, the mesenteric, and the renal. Below the 
coeliac axis the aorta divides, forming the right and the left 
common iliac which carry the blood to the lower limbs. 

Important Veins. — The blood from the lower limbs is 
conveyed to the abdominal region by means of the right 
and left common iliac veins, which unite to form the 
ascending vena cava. As this large tube passes upward 
it collects the blood from many smaller veins, the most 
important of which are the renal and the hepatic; the lat- 
ter are extremely short veins, three or four in number, 
which enter the vena cava just under the diaphragm and 
are almost surrounded by the liver tissue. 

After passing through the diaphragm the ascending vena 
cava pours its blood into the right auricle. The right and 
left subclavian veins, receiving the blood from the arms, 
unite with the right and left external and internal jugular 
veins of the neck to form the right and left innominate 
veins. These unite shortly to form the descending vena 
cava, which pours its blood into the right auricle, practically 
uniting with the ascending vena cava as it enters this cavity. 



CHAPTER XI 

THE BLOOD 

The Blood. — The reddish fluid which flows through the 
heart, arteries, capillaries, and veins is called blood. It is 
composed of solid particles called corpuscles, and a liquid 
portion known as the plasma. 

The Corpuscles. — It has long been known that the blood 
contains two distinct kinds of microscopic bodies. It was 
only recently that a third variety was discovered, which, 
although they are hardly true corpuscles, have been given 
the name platelets or plaques and are classified with the 
corpuscles. The small bodies, then, floating in the blood 
are the red corpuscles, the white corpuscles, and the plaques 
or platelets. 

The Red Corpuscles. — If a drop of blood be placed 
on a glass and put under a microscope of low power it 
is found to contain millions of small structures of strik- 
ingly uniform size and shape. These are the red corpus- 
cles. Careful examination shows that they are flat, disk- 
like bodies, rounded on the edge and concave on both 
sides. They are about one thirty-two hundredths of an 
inch in diameter and about one fifth as thick as they are 
broad. 

They tend to collect in rows in which they lie fiat 
against each other. When they are gathered together in 
large masses they appear red in color, but when observed 
alone they are greenish yellow in appearance. On account 

80 



THE BLOOD 



81 



of their bi-concave structure they appear to possess 
nuclei, but this appearance is deceptive as they are un- 
nucleated. 

It is estimated that there are about 30,000,000 red cor- 
puscles in a cubic inch of blood of the average adult per- 
son, with a total surface of 3,000 square yards. 

They are composed largely of water and albumen, with 
traces of salts and a small amount of an iron compound, 
hemoglobin, which probably gives it its color. When 
the hemoglobin comes in contact with the oxygen of the 
air it changes to oxyhemo- 
globin and causes a change in 
the color of the blood. 

The best authorities agree 
that the red corpuscles origi- 
nate in the red marrow of the 
bone, and that they possibly 
live from five to eight weeks 
before being worn out and 
thus rendered useless. When 
they can no longer perform 
their functions they are carried to the liver and spleen 
where they are decomposed. That the greater number are 
destroyed in the spleen seems evident from the fact that 
red corpuscles are found there in all stages of decompo- 
sition. Moreover, an excess of iron is found in the spleen, 
just as a large quantity of iron is found in -a farmyard 
where old implements have been piled up; the woodwork 
rotting away leaving the iron behind. 

The function of the red corpuscles in the blood is to 
carry oxygen. As suggested before, when the hemoglobin 
comes in contact with the oxygen the two unite to form 




Fig-. 42. — Red corpuscles. 

a, section through middle of red 
corpuscle. 



82 PHYSIOLOGY AND HYGIENE 

oxyhemoglobin. The oxyhemoglobin at the proper place 
in the tissues breaks up into oxygen and hemoglobin. 

White Corpuscles. — Under the microscope there may 
frequently be observed a few globular or irregularly shaped 
bodies called colorless or white blood corpuscles. These 
structures vary in size from smaller than the red corpus- 
cles to twice the size of the same, and are not only irregu- 
lar in shape, but pass through various forms even while 

being observed. As already ob- 
served, they are colorless and 
are unlike the red corpuscles in 
that they are nucleated. 

The white corpuscles are 
among the most interesting 
structures in the body, being 
very much like the amoeba 

Fig. 43. -white corpuscles. which we learned about earlier 

in the text. They have the 
power of throwing out projections, by means of which 
they are enabled to move slowly about in the blood or 
lymph. On account of this peculiar movement they are 
sometimes called wandering leucocytes. They not only 
have the power of locomotion, but are also able to bore 
their way through the thin walls of the capillaries and get 
into the lymph. 

The leucocytes increase by division, this development 
probably taking place in the lymphatic glands. There 
is one white corpuscle to every three or four hundred red 
ones. The white corpuscles have various functions: they 
destroy bacteria, eliminate waste matter from the system, 
and take part in the repair of wounded or diseased portions 
of the body. 




i m: blood 83 

Blood Platelets. — It has just been stated that the plate- 
lets or plaques have but recently been discovered. Upon 
first thought it might seem strange that these small bodies 
should have eluded observation for so long a time. How- 
ever, when we learn that the platelets disintegrate immedi- 
ately upon coming in contact with the air we can readily 
see why they were not observed sooner. 

The platelets are very small and are more nearly like the 
white than the red corpuscles. They are round to oval 
in form, pale in color, and are about as numerous as the 
white corpuscles. Their disintegration probably gives rise 
to the ferment that brings about coagulation. 

Plasma. — If the corpuscles be removed from the blood 
there remains a clear liquid called the plasma. This fluid 
portion of the blood is composed largely of albumens and 
water with traces of certain mineral salts. The albumens 
are of three kinds: fibrinogen, fibrinoplastin, and serum 
albumen. 

The quantities of these albumens in the blood are fairly 
constant and represent the food elements resulting from 
the digestion and absorption of the proteids. While all 
three of them furnish nutrition to the tissues, onfy the 
fibrinogen takes part in the formation of the fibrin of the 
clot. However, the presence of the fibrinoplastin seems 
absolutely necessary to the process of coagulation. As will 
be shown later, the serum albumen has nothing to do with 
this process. 

Coagulation. — The human body is subject to frequent 
injuries and dangerous wounds. If no provision were made 
on the part of nature for stopping the flow of blood in the 
event of a wound, bleeding to death would be a very com- 
mon occurrence. Nature, however, has provided a means 



84 PHYSIOLOGY AND HYGIENE 

of preventing excessive bleeding by clotting the blood 
whenever it comes in contact with the air. 

It was suggested in discussing the blood platelets that 
they disintegrate upon coming in contact with the air, pro- 
ducing a ferment which coagulates the blood. When this 
ferment is formed it immediately acts on the fibrinogen 
changing it from a liquid to threads of fibrin. These 
threads, however, can only be formed in the presence of 
the fibrinoplastin. The fibrin threads form a kind of 
mesh which entangles the corpuscles, thus forming the 
clot. As the clot develops it contracts, squeezing out 
the serum albumen and fibrinoplastin which constitute the 
so-called serum of the blood. If the break in the blood 
vessel is not too large the clot seals over the opening, thus 
preventing the loss of blood. 

Causes of Circulation of the Blood. — We have already 
learned that the function of the heart is to contract and 
send the blood out over the body. We have also learned 
that the heart is contracting only a part of the time, while 
we know that the blood is surging through the capillaries 
all the time. How can this continued flow of the blood 
through the capillaries be explained? 

It has been stated in discussing the arteries that their 
walls are very elastic. When the contraction of the heart 
drives the blood into the arteries under pressure their 
walls become distended, and when this contraction ceases 
the stretched elastic walls begin to contract, forcing the 
blood on through the capillaries in a fairly regular current, 
much as the compressed air in the chamber of a force 
pump drives the water out of the spout in a continuous 
stream. In studying the process of respiration we learned 
that the intercostal muscles and the diaphragm contract, 



THE BLOOD 85 

tending to produce a vacuum in the thoracic cavity. The 
tissues of the lungs being elastic, the pressure from with- 
out drives the air into the lungs. 

This fact gives us a suggestion as to another way in 
which the circulation of the blood is kept up. The pres- 
sure of the air on the body is transmitted to the veins, and 
when the pressure is removed from the heart by breathing, 
the blood is pushed slowly- toward that organ by this exter- 
nal pressure. Under these different influences the blood 
is urged slowly onward and the circulation is maintained. 

Pulmonary Circulation. — When the right auricle be- 
comes filled with the impure blood gathered from all parts 
of the body, the tricuspid valve opens and the blood drops 
into the right ventricle. The contraction of the heart then 
drives the blood out past the semilunar valves and through 
the pulmonary artery to the lungs. Here certain impu- 
rities are thrown out of the blood and oxygen takes their 
place. Being largely purified, the blood now sets back 
toward the heart through the pulmonary veins and collects 
in the left auricle. This movement constitutes the lesser 
or pulmonary circulation. 

Systemic Circulation. — While the impure blood is pour- 
ing into the right ventricle, the partially purified blood is 
dropping from the left auricle past the bicuspid valve into 
the left ventricle. The contraction of the heart forces the 
blood by the semilunar valves into the great aorta, whence 
it is driven through the many smaller arteries to all part? 
of the body. After passing through the great network of 
capillaries it is carried into the veins, through which it is 
conveyed slowly back to the right auricle. This great 
movement of the blood is called the systemic or greater 
circulation. 



86 PHYSIOLOGY AND HYGIENE 

Portal Circulation. — To assist in the process of absorp- 
tion and assimilation a special circulation has been devel- 
oped, known as the portal circulation. This takes place 
through the portal vein and its tributaries. In this circu- 
lation the venous blood is gathered from the stomach, 
spleen, and intestine by the gastric, splenic, and mesen- 
teric veins, which unite to form a large tube, known as the 
portal vein, which conducts the blood to the liver. After 
the blood filters through the liver tissue it is collected by 
the hepatic veins and poured into the ascending vena cava. 

Rate of Flow of Blood. — The rate of movement of the 
blood varies at different points in its progress. In the 
arteries the speed averages about sixteen inches per second, 
while in the capillaries it slows down to about one fiftieth 
of an inch per second. As the blood returns through the 
veins it flows on an average of about five inches per second. 
The blood passes through a complete circulation of the 
body in about thirty-two seconds. 

The Function of the Blood. — The liquid blood furnishes 
the one great means of communication between all parts 
of the body. As it keeps up its regular flow it conveys food 
particles and oxygen to build up cells and repair broken- 
down tissues. When old cells have been decomposed, the 
waste matter is thrown into the blood and carried to the 
organs of excretion, to be cast from the body. Moreover, 
as it flows by the centers of oxidation it takes in some of 
the resulting heat, conveying it to the external parts of 
the body, where it is dissipated. Being cooled, the blood 
flows once more toward the great centers, mingling its 
cool liquid with the hot blood of these regions. Not the 
least of the functions of the blood is that of equalizing 
the temperature of the body. 



THE BLOOD 87 

Anemia. — It has been shown that in healthy blood 
there are about three hundred red corpuscles for every 
white one. Frequently the relative number of red corpus- 
cles is less than the normal. In other cases the number 
may be up to the normal, but many of them are lacking 
in the important part called hemoglobin. In either case 
there is not sufficient hemoglobin in the blood to convey 
the required amount of oxygen to the tissues of the body. 
Such a disease of the blood is called anemia. 

Footnotes. — l The blood of many animals, including man, is always 
warm in life, no matter what the temperature of surrounding objects 
may be. Animals of this kind are called warm-blooded animals. 
Their temperature does not vary far from 100°. In some animals, 
however, the temperature of the blood ranges from below freezing 
point to 90°. In these animals the temperature of the blood be- 
comes, after a short time, the same as that of surrounding objects. 
These are called cold-blooded animals and include reptiles, frogs, 
and fishes. 

2 Boils are caused by the accumulation of white corpuscles under the 
skin. The leucocytes gather poisonous matter from the system, and 
collect at some point on the surface, where they break through. 



CHAPTER XII 

THE LYMPH— NARCOTICS 

Lymphatic System. — We have already learned that a 
part of the blood sent out from the heart is returned to that 
organ by the veins. Not all of the blood, however, finds 
its way back through these tubes. Placed throughout 
the system in an irregular fashion is a second set of tubes 
which serve a purpose similar to th^t of the veins. As the 
blood forces its way through the small capillaries some 
of the plasma with a few white corpuscles passes through 
the thin walls and begins its slow journey back toward the 
heart. This movement takes place through the lymphatic 
system. 

Lymph Spaces. — The blood capillaries are in close con- 
tact with the different tissues and cells of the body. Be- 
tween these tissues and cells are small irregular spaces, 
into which the nutritious plasma of the blood soaks. From 
these irregular cavities the cells absorb the food elements 
necessary to their growth or repair. Inasmuch as these 
cavities constitute the beginning of the lymphatic system, 
they are called lymph spaces. 

Lymph Capillaries. — The irregular lymph spaces open 
out into minute, thin-walled, well-defined tubes known as 
lymph capillaries. From the lymph spaces the lymph 
passes into these capillaries. 

Lymph Veins. — The lymph capillaries collect the lymph 
from the lymph spaces, and, uniting with other capillaries, 

88 



THE LYMPH NARCOTICS 



89 



MEDIASTINAL 
LYMPHATIC VESSEL 



pour their contents into larger tubes called lymph veins. 
These are very much like ordinary blood veins, having 
three well-defined coats, and possessing valves opening 
toward the heart. 

Receptaculum Chyli. — 
The lymph veins collect the 
lymph from the lower part 
of the body and from the 
lacteals, and unite in the 
upper part of the abdomen 
to form the receptaculum 
chyli. The lymph veins do 
not unite to form larger 
tubes as do the blood veins, 
but all pass to the bulb- 
shaped receptaculum chyli, 
into which pours the lymph. 

Thoracic Duct. — At its 
upper end the receptaculum 
chyli narrows into a small 
tube called the thoracic 
duct, which passes upward 
toward the lower part of 
the neck, where it receives 
the lymph from the left 
shoulder and neck, and, 
making a quick turn, unites 
with the left 'subclavian 
vein at its junction with the 
left internal jugular vein. 

Right Lymph Duct.— The 
lymph veins from the right 




LACTEAL 



OPHAGUS 



DESCENDING 
THORACIC 
LYMPHATIC TRUNK 



LACTEALS 



OMMON LUMBAR 
YMPHATIC TRUNKS 



Tig. 44. — Lacteals and receptaculum. 
chyli, thoracic duct. 



90 PHYSIOLOGY AND HYGIENE 

neck, shoulder, and thorax unite to form the right lymph 
duct, which pours its lymph into the right subclavian vein. 
Thus we see that a portion of the blood finds its way back 
to the heart through the lymph tubes. 

Lymphatic Glands. — At intervals the lymph filters 
through bean-shaped nodules along the veins which, from 
a certain likeness to true glands, are called lymphatic 
glands. These nodules are composed of meshes of connec- 
tive tissue, among which are found numerous white blood 
corpuscles. It is thought that these glands are the seat of 
the cell division of the white corpuscles. 

Uses. — It is believed that these glands serve as central 
stations or " roundhouses," from which the leucocytes are 
sent in case of emergency or accident to assist in repair or 
construction work. 

Lymph. — It has already been suggested that the lymph 
is composed largely of blood plasma and white blood cor- 
puscles. It is a clear, watery fluid except where it is filled 
with fatty particles as it passes through the lacteals. 

Lymph Movement. — While the process of respiration 
may have a slight effect on the movement of the lymph, this 
movement is due principally to the contraction of the 
muscular tissues and the ordinary motions of the body. 
As a muscle contracts, pressure is exerted upon the lymph 
tubes and the lymph is pushed slowly forward. The pres- 
ence of the valves in the veins prevents the return of the 
lymph, and as a result of these conditions it moves forward 
in a slow, sluggish stream. The movement is much more 
rapid when the body is in motion, hence the necessity for 
proper exercise. 

Function of the Lymph. — The lymphatic system is 
essentially a sewerage system, inasmuch as it receives and 



THE LYMPH— NARCOTICS 91 

carries off the overflow from the blood. The lymph, how- 
ever, bathes all the softer tissues of the body, thus bring- 
ing nutrition closer to the cells than the blood could do. 
The lymph carries food elements from one part to another 
and conveys waste matter away from disintegrated tissues 
to be eliminated from the body. The white corpuscles 
assist in repairing wounded or diseased parts and destroy 
bacteria. 

Alcohol and the Blood. — Alcohol extracts water from 
the red corpuscles, depriving them of the power of carry- 
ing oxygen. Imagine millions of these corpuscles shrunken 
and dried up as a result of the action of alcohol, and you 
can readily see what the effect would be on the nourish- 
ment of the tissues of the body. The blood no longer 
contains a sufficient supply of oxygen. 

Alcohol and the Blood Vessels. — Alcohol destroys the 
elasticity of the muscle fibers in the walls of the veins and 
arteries and paralyzes the nerves that supply them. Con- 
sequently the blood rushes through the enlarged tubes to 
the surface of the body, where it liberates an abnormal 
quantity of heat. The continued use of alcohol leaves 
the blood vessels permanently enlarged, a condition that 
gives rise to the red nose and flushed face of the drunkard. 

Alcohol and the Heart. — But the Worst effect is observed 
in the case of the heart. The cells once broken down can- 
not be rebuilt in the presence of alcohol. In the place of 
the decomposed cells is deposited fatty tissue. This deposit 
leads to the condition known as " fatty degeneration,'' a 
condition in which a large number of the cardiac muscle 
fibers are replaced by cells of fat. It is evident that the 
energy of the heart is much decreased and that it is no 
longer able to do its work fully. That this is true may 



92 PHYSIOLOGY AND HYGIENE 

be proved by placing the ear over the heart thus affected 
and observing the weak, languid heart throbs. 

Tobacco and the Circulation. — Tobacco destroys the 
vitality of the blood much as does alcohol. It affects the 
regularity of the heart's beat, producing palpitation of that 
organ. Men who have used tobacco for a long time often 
suffer from the disease known as "tobacco heart/' a dis- 
ease that is responsible for many cases of so-called heart 
failure. 



CHAPTER XIII 

DIGESTION— THE MOUTH 

How the Body Grows. — We have already learned that 
all organized bodies develop from a very few cells. How 
this development takes place is one of the mysteries of 
nature. To secure material for this growth it is necessary 
that all living bodies take into their organism food parti- 
cles of various kinds. How these food particles enter into 
the structure of different organs is not fully known. No 
one has yet been able to tell how certain elements taken 
into the body produce in one case feathers, in another, 
hair, and yet in another, wool. Science has not yet dis- 
covered how it is possible for corn to enter into the body 
of the cow to produce beef, and on the other hand to enter 
into the body of the hog to produce pork. 

It is sufficient for us here to learn something of those 
processes by means of which food particles are taken into 
the body and built into its living tissues. These processes 
are known as digestion, absorption, and assimilation. To 
carry on these processes specialized organs have been de- 
veloped in the system. 

Organs of Digestion. — The lower the animal is in the 
scale of life the less highly developed are all its organs. 
The amoeba uses the external portion of its body for its 
skin, its feet, and its stomach. When it comes in contact 
with a food particle its body surrounds it, and what was 
the exterior wall now becomes the lining of the stomach. 

93 



94 



PHYSIOLOGY AND HYGIENE 



Here the particle is digested, the nutritious portion 
absorbed, and the waste matter ejected, after which the 
amoeba resumes its usual shape. 

More highly organized animals have a more complex 
digestive apparatus. In some, however, this consists of a 
mere tube passing through the body through which the 
food is carried, and from which the nutritive elements 
are absorbed and the waste products eliminated. In the 
highest forms as in man we find an extremely complicated 
digestive apparatus. In the human being this consists of 
a long tube called the alimentary canal. 

This tube has a number of modifications which have been 
developed to perform some particular function. These 

are the mouth, the 
teeth, the tongue, the 
oesophagus, the stom- 
ach, and the large and 
small intestines. A 
number of other or- 
gans which are con- 
cerned directly with 
digestion will be dis- 
cussed in their proper 
places. The alimen- 
tary canal is from 
twenty-five to thirty 
feet long. 

larynx The Mouth Thp 

'ESOPHAGUS ine moum - _ ine 

Tig. 45. — Mouth, showing teeth and tongue mouth is a cavity ly- 

in position ' ing in the lower front 

part of the head, and has six openings besides the ex- 
terior: two posterior nares, two eustachian tubes, the 



OPENING OF 
EUSTACHIAN TUB 



SOFT PALATE 
PHARYNX _ 

EP1GL0TTIS_ 



ASALCAVITY 



^X-^MaTiJARD PALATE 




TONGUE 



DIGESTION— THE MOUTH 



95 



pharynx, and the larynx. The mouth is fairly large 
in size, but when closed is usually filled by the tongue. 
It is bounded in front and on the sides by the lips, 
teeth, and cheeks. 



..ENAMEL 



TEETH— THEIR VALUE AND HOW TO 
CARE FOR THEM 

By Win. R. Wright, D. D. S., 1 ex-Secretary Mississippi Board of 
Dental Examiners, ex-President Mississippi Dental Association. 

Anatomy of the Teeth. — Human teeth are fitted into 
sockets of the jaw bones. The sockets are lined with 
a membrane connected and con- 
tinuous with the gum. That 
part of the tooth below the gum 
is called the root, and the por- 
tion out of the gum is the crown. 
The dividing line between the 
two at the gum is the neck. The 
tooth is composed largely of 
three hard tissues, enamel, den- 
tine, and cementum. In the 
middle of the tooth and extend- 
ing through its long axis is 

the nerve or pulp, a fibrous mass of nerve matter 
and blood vessels. The dentine forms the main 
portion of the tooth. The enamel is the hardest 
substance in the body and forms a protective cov- 
ering for the crown. The roots of the teeth are cov- 
ered by a substance closely resembling bone, called ce- 

1 The author gratefully acknowledges valued assistance from Drs. J. F. Scott and 
Heuel May, and Deans William Crenshaw, of Atlanta Dental College and Andrew 
G. Friedrichs, of New Orleans College of Dentistry. 




Fig-. 46.— Structure of a 
tooth. 



96 



PHYSIOLOGY AND HYGIENE 



mentum. The nerve and blood vessels enter the ends 
of the roots and give nutrition and sensation to the teeth. 
Names of the Teeth. — The first, or temporary, set 
has in each jaw three groups: four front teeth, or 
incisors, so called from their sharp, chisel-like edges; 
two cuspids, one on each side, so called because they 
have one cusp or raised portion; and four molars, 
two on each side. In the permanent set (Fig. 48) 
the teeth which take the places of temporary molars 
are called bicuspids because they have two cusps or 
raised portions. As the jaw bone grows other teeth, 
called molars, grow in back of the temporary teeth. 

The first of these 
to appear in each 
jaw are the sixth- 
year molars, so 
called because 
they come about 
the child's sixth 
year, one on each 
side. Later, an- 
other molar de- 
velops on each 
side, and, finally, 
the "wisdom" 
teeth, so called because they come later in life. The 
set of permanent teeth is thus complete, making 
sixteen in each jaw, or thirty- two teeth in the 
mouth. 

Formation and Eruption. — Every normal person has 
two sets of teeth, the deciduous or temporary teeth, 
twenty in number, and the permanent teeth, thirty-two 








Fig. 47, 



-Showing temporary teeth with sixth- 
year molars. 



DIGESTION— THE MOUTH 



97 



.-.INCISORS 



CUSPID 



...BICUSPIDS 



.MOLARS 



in number. The germs of both sets of teeth exist in the 
cells of the jaws from earliest infancy. 

The temporary teeth begin to erupt, or appear, al- 
most always in front in the lower jaw about the child's 
fifth month. 

The permanent teeth have their starting point 
above the temporal teeth in the upper jaw and be- 
low the temporary 
teeth in the lower 
jaw, ready to fol- 
low the temporary 
teeth and take 
their places when 
the members of 
the first set are 
lost because of the 
absorption of their 
roots. There are 
exceptions to this 

rule. One very important exception is found in the 
sixth-year molars, the first permanent jaw teeth, which 
come just back of the temporary teeth, and do not dis- 
place any teeth, but take their positions, one on each 
side, above and below (Fig. 47). They are important, 
because they articulate, the upper with the lower, and 
hold the jaws in proper relation to each other while 
, the other permanent teeth are taking their positions 
in the jaw. They are also important on account of 
their broad masticating surfaces, enabling us to chew 
our food, though a number of temporary teeth may 
have been lost. Too much care cannot be taken to 
save the first molars. The loss of one or more of the 




Fig-. 48.— Upper permanent teeth. 



98 



PHYSIOLOGY AND HYGIENE 



sixth-year molars means a crippled mouth for life. 
The dentist should be consulted from time to time to 
prevent decay or loss of any of these teeth. The 
second or twelfth-year molars and " wisdom" teeth 
also appear in the jaw without displacing any tem- 
porary teeth. (Fig. 48.) The growth of the jaw bone 
makes room for the several molars as they come and 
also for the larger permanent teeth as they displace 
the temporary teeth in front of the molars. 

How Teeth Occlude or Fit Together. — The teeth of the 
upper and lower jaws are so adjusted that the cusps or 

elevations of the bi- 
cuspids and molars 
of one jaw fit into 
the depressions of 
those of the oppo- 
site, thus enabling 
us to grind our food 
into fine particles 
before it is passed 
into the stomach for 
digestion. The in- 
cisors and cuspids 
are so adjusted as 
to enable us to bite 
or tear our food before it is masticated by the other 
teeth. 

The Function or Use of the Teeth. — The uses of the 
teeth are varied and important. They enable us to 
chew or grind our food into fine particles and to mix it 
with the saliva of the mouth, the first of the digestive 
fluids, thus greatly facilitating the process of digestion. 




Tig. 49.— Showing- how teeth fit tog-ether. 



DIGESTION— THE MOUTH 99 

They aid us in pronouncing words, and when cared for 
properly they give beauty and expression to the face. 
If the teeth are irregular, or illy kept, they detract 
greatly from the facial expression. On the other hand, 
nothing could lend more attractiveness to one's face 
than a well-formed mouth of regular, clean teeth, set 
in healthy pink gums. 

Effect of Teeth on the Health. — Without good, 
healthy teeth, perfect mastication and digestion are im- 
possible and without these perfect health is impossible. 
Inasmuch as our future happiness is largely affected by 
our physical health it is highly important that we give 
such early and diligent care to the teeth as will insure 
their unimpaired usefulness. 

The condition of the teeth has such an important 
bearing upon health that the United States Government 
requires every applicant for enlistment in the Army 
to submit to a careful examination of the teeth, and 
in case they do not come up to a certain standard 
the applicant is rejected. Competent dentists are 
employed to look after the teeth of those who are re- 
ceived into the army. These prescribe such measures 
as will keep the mouths and teeth of the soldiers in a 
healthy condition. Careful examination of the mouths 
of the children in the public schools of some of our 
larger cities has disclosed the startling fact that com- 
paratively few children have perfectly sound, healthy 
teeth. It has also been discovered that on account of 
the poor health of these children they are irregular in 
attendance and backward in their studies. It is prob- 
able that this condition would not exist if the teeth of 
these children had received the right kind of attention. 



100 PHYSIOLOGY AND HYGIENE 

These facts emphasize the importance of early and 
persistent care of the teeth to the end that, with the 
aid of sound bodies, the highest standard of mental, 
moral, and physical development may be attained. 

The Loss of the Teeth. — Temporary teeth are lost in 
the natural way through the absorption of their roots, 
but they are sometimes lost through neglect which leads 
to decay. 

Permanent teeth are lost mainly through diseases of 
the gums and through decay. Of each one hundred 
missing teeth approximately sixty are lost from dis- 
eased gums, and forty from decay. If the mouth is 
neglected, tartar, a hard substance deposited by the 
saliva, accumulates around the necks of the teeth, 
irritates the gums, and finally absorbs the alveoli 
process, or bony support of the teeth, which may be- 
come loosened and fall out. 

The loss of even one tooth means a serious handicap 
in the process of mastication because we not only lose 
the use of the missing tooth and its opposite, but the 
efficiency of the one on either side of the vacancy is 
greatly impaired. 

Causes of Decayed Teeth. — Teeth decay mainly be- 
cause they are not kept clean. Particles of food cling 
to the teeth, find lodgment between them, or are 
packed into the pits or depressions in imperfectly de- 
veloped teeth. If these particles are not removed, fer- 
mentation sets up and the acids formed attack and dis- 
solve the enamel of the teeth, exposing the dentine, and 
decay results. The enamel may also be injured by 
using, as a toothpick, some metallic instrument , or by 
cracking nuts, or by biting other hard substances with 



DIGESTION— THE MOUTH 101 

the teeth, thus opening the way to the dentine with 
the result that decay soon follows. 

Care of the Temporary Teeth. — Uninformed persons 
are apt to think that it is not important to try to pre- 
serve the temporary teeth, because they are only tem- 
porary. This is a great mistake, for the child needs 
the use of the teeth and, besides, their preservation 
conforms to nature's plan and insures a better and 
more regular set of permanent teeth. Furthermore r 
these "human pearls" should be saved for their beauty. 
For these reasons the temporary teeth should be cleaned 
and watched with the same degree of diligence as 
though they were permanent . In cleaning them a child ' s 
brush with a limited number of bristles should be used, 
and the movement of the brush should be upward and 
downward in order to facilitate the removal of all for- 
eign substances from between the teeth. 

How Teeth May Be Preserved. — The first consider- 
ation in preserving the teeth is to keep them clean, be- 
cause clean teeth do not decay. Particles of meat and 
other organic matter should be removed from between 
the teeth and from the irregularities of their surfaces. 
The toothbrush should be selected with care and should 
contain bristles of uneven lengths so that by brushing 
the teeth from the gums toward the crowns these 
bristles will remove all foreign substances. The teeth, 
should be carefully brushed three times daily, prefer- 
ably after each meal. 

Tooth powders and similar preparations should be 
avoided unless recommended by the family physician 
or dentist, because they may contain acids that are in- 
jurious to the enamel. It does not require a specialist 



102 PHYSIOLOGY AND HYGIENE 

to explain why powders containing pulverized pumice 
stone, or other gritty substances that wear away the 
enamel, should not be used. 

The dentist should inspect the teeth at least twice 
each year to remove any deposited tartar and to fill any 
small cavities that may have formed. This careful 
attention will help ward off suffering, and is less expen- 
sive than neglect and procrastination. 

Irregular Teeth. — Irregular teeth are due to several 
causes, the most important of which are abnormal or 




Before treatment. After treatment. 

poor development of the upper and lower jaws, and also 
to obstructions of the nasal passages, usually adenoids. 
Too early extraction of the temporary teeth, as well as 
delayed extraction, has an important bearing upon the 
positions of the permanent teeth. Remarkable im- 
provements can be made; in fact, one's facial expression 
may be entirely changed by the dental specialist in this 
work, who should be consulted if irregularities of the 
teeth are discovered. These irregularities should be 
corrected not only for the purpose of improving the 
appearance of the face, but for the purpose of preserv- 
ing the teeth to the end that the food may be fully 
masticated. 



DIGESTION— THE MOUTH 



103 



TONSIL 



FUNGITO 



IRCUMVALLATE 



The Tongue. — This organ is a large, conical-shaped 
muscle, the base of which is attached to the hyoid bone. 
The small, free end lies toward the front of the mouth 
and has great freedom of motion. The upper surface 
of the tongue is covered with many small projections 
called papillae. ^ .e^q ths 

There are three 
kinds of these 
projections, 
known as the fili- 
form, fungiform, 
and circumval- 
late papillae. 

The filiform are 
threadlike projec- 
tions which make 
the tip of the 
tongue very sensi- 
t i v e to touch 
since they are 
found principally 
toward the end of 

that Organ. I he Fig-. 50 — Tongue, showing tonsil and papillae. 

fungiform are 

scattered all over the surface of the tongue and take their 
name from their similarity to mushrooms. The fungi- 
form papillae are the important organs of taste. On the 
back of the tongue are located eight to twelve large 
structures called circumvallate papillae. They are ar- 
ranged like the letter V, with the point toward the rear. 
At the back of the tongue on each side is an enlarge- 
ment known as the tonsil. A branch of one of the 




104 



PHYSIOLOGY AND HYGIENE 



cranial nerves, usually styled the gustatory nerve, sends 
fibers to the front part of the tongue, while a branch 
of the glossopharyngeal nerve supplies the back portion. 

The Functions of the 
Tongue . — The func- 
tions of the tongue are 
varied. It assists in 
rolling the food about 
in the mouth and mix- 
ing it with the saliva. 
It helps mold the food 
particles into balls or 
pellets to be swal- 
lowed. On account of 
its extreme sensitive- 
ness it is able to locate 
fragments of food fas- 
tened between the 
teeth and assists in 
dislodging them. It 
serves as the organ of 
taste as well as an organ of touch. Finally, it aids 
in modifying the voice, being considered as one of 
the organs of speech. 

The Salivary Glands. 1 — There are three pairs of 
salivary glands. The parotids lie at the back of the 
jaw, one on each side, and have ducts that open into 

1 Usually, at some time during the period of childhood the parotid 
glands, and occasionally the others, become swollen. The swelling 
is preceded by pain, and appears close to the ear behind the jaw. 
Generally the swelling of the glands on one side precedes that on the 
other by two or three days. This is a disease called mumps, and, with 
rare exceptions, is not dangerous. 




Tongue. 



DIGESTION— THE MOUTH 



105 



the mouth at the base of the upper molar teeth. The 
submaxillary glands are located under the back of the 
jaw; their ducts open at the sides of the tongue. A 
pair of glands, called the sublinguals, lie under the jaw, 
the ducts of which enter under the tongue. The salivary 
glands are compound structures and secrete the saliva, 
the only digestive 
juice of the mouth. 

The Saliva. 1 — This 
secretion is com- 
posed largely of wa- 
ter. It is a clear, 
ropy, alkaline liquid, 
a little heavier than 
water. Its stickiness 
is due to the pres- 
ence of a small quan- 
tity of a mucilagi- 
nous substance 
known as mucin. 
The only important 

digestive agent in the saliva is the ferment, ptyalin. 
The saliva contains a small quantity of mineral salts. 2 

The Saliva as a Digestive Agent. — Since the only active 
principle in the saliva is the ptyalin, its function as a 
digestive fluid is not great. The ptyalin acts on 

1 The simple act of chewing causes a flow of the saliva. The habit 
of chewing gum is injurious, inasmuch as it causes an abnormal secretion 
of the saliva when it is not needed. 

2 In addition to those substances mentioned above as being found 
in the saliva, there are occasionally observed a few leucocytes, or 
white blood corpuscles. These leucocytes have evidently wandered 
through the walls of the capillaries in the mucous membrane of the 
mouth and dropped into the saliva. They have no use at this point. 




SUBMAXILLARY, 

GLANO 

SUBLINGUAL GLAND/', 



Fig-. 52.— Salivary glands. 



106 PHYSIOLOGY AND HYGIENE 

the starches, changing them into sugar. Since the 
starches are insoluble, they must be reduced to a 
soluble form before they can be absorbed. The ptyalin 
effects this change. However, only a small quantity of 
the starches are digested at this point. The remaining 
portions are rendered soluble by the amylopsin of the 
pancreatic juice in the small intestine. It is worth 
while to observe that the ptyalin would not act were 
it not for the fact that the saliva is alkaline. 

Other Functions of the Saliva. — In addition to its use as 
a digestive agent, the saliva serves other purposes. In 
the first place, it dissolves food particles that are not 
already in the soluble form, such as sugar, salt, etc. Be- 
sides, it moistens the mucous membrane of the mouth. 
The secretion from the mucous glands here would not 
be sufficient to keep the membrane soft and moist 
when dry food, such as crackers, is taken into the mouth. 
Imagine one who tries to swallow dry cracker crumbs 
from a perfectly dry mouth. The saliva acts as a general 
solvent and moistening agent for the mixing of the food. 

Digestion in the Mouth. — When the food is taken into 
the mouth it is thoroughly chewed up and ground 
into fine portions by the teeth. This process is called 
mastication. By means of the tongue, teeth, and cheeks 
it is rolled about and mixed with the saliva, a process 
known as insalivation. While these processes are going 
on the starches are being attacked by the ptyalin, which 
changes a portion of them into soluble sugar. When the 
food is ready to leave the mouth it is rolled into small 
pellets, and conveyed to the back portion of the mouth, 
where it is seized by the upper part of the oesophagus 
and pushed down this tube into the stomach. 



CHAPTER XIV 

DIGESTION— THE STOMACH 

(Esophagus or Gullet. — The oesophagus is a muscular 
tube about nine inches long, extending from the pharynx 
to the stomach. In its normal condition it is the smallest 
portion of the alimentary canal, being narrowest at its con- 
nection with the pharynx. It is composed of three coats, 
and is covered by a so-called fourth coat, which in the tho- 
racic cavity is called the pleura, and below the diaphragm, 
the peritoneum. When not distended with food its inner 
surface is thrown into longitudinal folds, which disappear 
during swallowing. 

Muscular Coat. — Lying under the pleura and the peri- 
toneum as indicated above is the outer or muscular coat. 
This is a thick layer composed of two divisions, in the outer 
of which the muscle fibers are arranged longitudinally, in 
the inner of which they are arranged circularly. This per- 
mits of both a lateral and a longitudinal motion. Between 
the two layers of muscle fibers are numerous blood vessels, 
nerves, and ganglia that nourish and innervate the walls 
of the gullet. 

From the function of the oesophagus one would expect 
to find these muscular walls made up entirely of the plain 
muscle fibers, but investigation proves that the muscular 
tissue of the upper portion is red and consists largely of 
striated muscle fibers, which give way lower down to the 
plain muscle fibers. This explains the fact that we have 

107 



108 PHYSIOLOGY AND HYGIENE 

some control over the upper part of the oesophagus, but 
lose this control entirely in the lower portion. 

Areolar Coat. — This coat is a loosely constructed layer 
of connective tissue that holds the mucous coat to the 
muscular coat. It contains some ganglia and nerves. 

Mucous Coat. — This lines the inner surface of the 
gullet, and is composed of mucous membrane carrying 
several layers of epithelial cells. The longitudinal folds 
mentioned above are merely folds of the mucous mem- 
brane alone. Between the mucous and the areolar coats 
is a thin layer of plain muscle fibers arranged longitudi- 
nally. This layer, while almost wanting at the upper end 
of the oesophagus, is fairly thick toward the stomach. 

Use of the (Esophagus. — The oesophagus receives the 
food from the pharynx and conveys it to the stomach. 
This is accomplished by a relaxation of the muscle fibers in 
front of the food and a contraction of the same behind, 
the food being pushed rapidly forward through the tube 
into the stomach. 

The Stomach. 1 — This organ is a large expansion of the 
alimentary canal lying in the upper left side of the abdomen. 
In this connection it might be well to know what the abdo- 
men is. The abdomen is the largest cavity in the body. It 
contains a number of organs, especially those of digestion 

1 Such herbivorous animals as the cow and sheep have four stom- 
achs, or rather one stomach divided into four distinct compart- 
ments. It is worthy of note that scientists teach that digestive 
organs which are not used will in time disappear. The digestion 
of the grass and fodder which the cow eats demands a more com- 
plicated digestive apparatus than is necessary in man. To supply 
this demand the above arrangement of the stomach is developed. 
We are told that if we continue to eat predigested foods, thus rob- 
bing the stomach of its work, it may finally decrease in size and 
disappear altogether. 



DIGESTION— THE STOMACH 



109 



PHARYNX 



and excretion. It occupies the lower portion of the trunk and 
is separated from the thoracic cavity above by the diaphragm, 
a thin muscular organ curved upward. The abdomen is 
lined throughout with a serous membrane called peritoneum. 
As already stated, the stomach lies in the upper left 
side of this cavity, the 
corresponding right side 
containing the liver. 
The stomach connects 
with the oesophagus at 
the cardiac orifice, a 
point lying close under 
the heart beneath the 
diaphragm. The stom- 
ach is a baglike struct- 
ure varying in size, 
averaging about ten 
inches long and six 
inches wide. It has a 
short, downward curve 
on its upper surface and 
a larger, wider curve on 
the left and under side, 
called the fundus. It 




Fig. 53. — (Esophagus and stomach. 



is narrowed toward the right and connects with the small 
intestine at the pyloric orifice, an opening usually closed 
by the so-called sphincter muscle. 

Structure of the Stomach. 1 — The stomach is covered with 

1 The great omentum serves an important function in protecting 
the delicate digestive apparatus from sudden changes of tempera- 
ture. In this mesenteric apron is lodged a great accumulation of 
fat which covers the front of the abdominal cavity and keeps the 
inclosed organs warm. 



110 PHYSIOLOGY AND HYGIENE 

a layer of peritoneum, the serous membrane already men- 
tioned, a fold of which hangs over the front of the stomach 
as the great omentum. Under the peritoneum is the real 
outer layer of the stomach, the muscular coat. It is similar 
to the corresponding coat in the oesophagus, inasmuch as: 
it has the outer layer of fibers arranged longitudinally and 
the layer of circularly arranged fibers within the outer. 
It has in addition, however, an inner -layer, in which the 
fibers are placed obliquely. This complex arrangement of 
the muscle fibers makes it possible for the stomach to con- 
tract in all directions during the peristaltic action . The 
areolar coat is a continuation of that structure in the 
oesophagus and serves a like function. 

It is in the mucous coat that we observe the greatest 
difference. This is a thick, soft, velvety, reddish-tinged 
membrane covered throughout with a siogle layer of 
epithelial cells. Extending into the membrane from the 
cavity of the stomach are many small tubes called gastric 
glands. These glands are lined with epithelial cells, which 
since they are supposed to secrete the pepsin of the gastric 
juice are here called peptic cells. Under the peptic cells 
lie a few others irregularly placed which secrete the hydro- 
chloric acid of the gastric juice; these are the oxyntic 
cells. 

Gastric Juice. 1 — The digestive agent in the stomach is 
secreted by the gastric glands described above, and is 

1 Often a sharp, burning sensation is experienced in the oesophagus. 
This is caused by the acid contents of the stomach being forced 
up into this organ. As the sensation is felt close to the heart, it is- 
called heartburn. Sometimes bile is driven from the duodenum 
into the stomach, and from that point forced up into the back part 
of the mouth, causing a bitter taste. This is another form of heart- 
burn. 



DIGESTION— THE STOMACH 



111 



DUCTS 



called the gastric juice. It is composed of about ninety- 
nine per cent of water and one per cent of hydrochloric 
acid, pepsin, mineral salts, and rennin in about equal 
proportions. 

Gastric Digestion. — The food is carried to the stomach 
by the oesophagus, where it is attacked by the gastric juice. 
The muscle fibers of the walls contract, producing the 
characteristic churning motion called peristalsis. This 
process stirs the food 
iip, mixing it with the 
gastrie juice. 

The alkaline condi- 
tion produced by the 
saliva now gives way to 
the acid condition due 
to the presence of the 
hydrochloric acid, and 
the action of the ptyalin 
is stopped. The pepsin 
attacks the insoluble 
proteids and albumin- 
oids, changing them in- 
to soluble peptones and 
gelatine. 

As already stated, the hydrochloric acid renders the con- 
tents of the stomach acid, since pepsin can act only in an 
acid solution. The hydrochloric acid dissolves the solid 
mineral salts, rendering them soluble. In addition to this 
the acid destroys disease germs that enter the stomach. 
Neither the fats nor the starches are digested here. The 
function of the rennin is not fully understood, but it tends 
to coagulate milk. 




Pig-. 54. — Gastric gland. 



112 PHYSIOLOGY AND HYGIENE 

After the food has remained in the stomach for a suf- 
ficient time, usually from two to four hours, and the gas- 
tric digestion is complete, the sphincter muscle surround- 
ing the pylorus relaxes and the digested material is pushed 
into the duodenum. 



CHAFFER XV 



DIGESTION— THE INTESTINES 



The Small Intestine. — The small intestine is a slender 
convoluted tube, from twenty to twenty-five feet long, 
folded in the abdominal cavity. It is held in place by the 
large intestine at the sides and 
above, and in front by the 
great omentum and the ab- 
dominal wall, being suspended 
from the spine by a sling or 
fold of peritoneum, called the 
mesentery. It is divided into 
three parts: the duodenum, 
the jejunum, and the ileum. 

The duodenum is about ten 
or twelve inches long and is 
horseshoe in shape, inclosing 
a portion of the pancreas in 
the curve. About four inches 
from the pylorus is an open- 
ing which admits the bile 
and the pancreatic juice. The 
jejunum is a continuation of 
the intestine from the duo- 
denum, and is from eight to * SE?A**^.!S^ 
ten feet long, varying, how- 
ever, in length. The division 

113 




Fig. 55. — Stomach and intestines. 



intestine; g, h, i, large intestine; j, 
location of illeo-colic valve ; k , vermi- 
form appendage; I, caecum; m, por- 
tion of sigmoid flexure. 



114 



PHYSIOLOGY AND HYGIENE 



between the jejunum and the ileum is not clear cut, the 
length of the two portions varying in the same individual. 
The ileum is supposed to commence at the point where the 
putrefaction of the food begins and includes the remaining 
portion of the small intestine, uniting with the large intes- 



VILLI 




Fig. 56. — Section of ileum magnified. 



tine in the lower right-hand section of the abdomen. The 
small intestine contains many folds and convolutions 
throughout its entire length. These folds are especially 
prominent in the ileum. 

Structure of Small Intestine. — The small intestine is in- 
closed in a covering of peritoneum. Beneath this is found 
the typical muscular coat made up of two layers, the outer 
containing the fibers running longitudinally, the inner be- 
ing made up of fibers arranged circularly. The areolar 
coat is present, holding the mucous coat to the muscular. 
The inner coat, the mucous, is thick and vascular toward 
the beginning, but becomes paler and thinner toward the 
large intestine. The mucous membrane of the small in- 



DIGESTION— THE INTESTINES 115 

testine contains many modifications which fit it for diges- 
tion and absorption. 

Modifications of Mucous Membrane. — The valvulse con- 
niventes are foldings not only of the mucous coat but also of 
the areolar. They are ridges on the inner surface of the in- 
testine that extend about two thirds of the way around the 
tube and are one third of an inch or less in height. These 
ridges are not all of the same size and the large and small 
usually alternate with each other. The valvule conniventes 
tend to keep the food from moving too rapidly and afford a 
large surface for absorption. The soft velvety feel and ap- 
pearance, mentioned in connection with the mucous mem- 
brane of the stomach, are duplicated in the small intestine. 

Under the microscope the entire surface is seen to be 
covered by little projections called villi, that contain a 
number of structures of interest. They are larger and 
more numerous in the duodenum and jejunum, the total 
number in the whole tube being estimated at over four 
millions. Each villus is covered with a single layer of epi- 
thelium and contains lacteals, arteries, veins, plain muscle 
fibers, and nerves. These villi are the organs of absorption. 

The crypts of Lieberkiihn are glands scattered among 
the villi, having a structure and appearance similar to those 
of the gastric glands. They secrete the intestinal juice, the 
composition and function of which have not been fully 
determined. Scattered among the villi and the crypts 
of Lieberkiihn are many nodules of fymphoid tissue, 
which vary from a minute particle to an aggregation an 
inch or more long, and are called patches of Peyer. 1 Neither 
villi nor crypts are found on the surface of these patches. 

typhoid fever is believed to be carried by myriads of bacteria feed- 
ing upon these patches. 



116 PHYSIOLOGY AND HYGIENE 

The Large Intestine. — The large intestine is a wide, 
baggy tube that connects with the ileum in the lower right 
side of the abdomen and, passing upward, crosses under the 
liver, descending on the left side. It is about five feet long, 
and in its passage it forms a curve that almost surrounds- 
the convolutions of the small intestine. Beginning with 
the vermiform appendage, we find the large intestine con- 
tinued through the caecum, the ascending colon, the trans- 
verse colon, the descending colon, and the sigmoid flexure. 

The vermiform appendage is a small tubular structure, 
four or five inches long and somewhat smaller than a lead 
pencil. It is worm shaped in appearance and its tube 
opens into the caecum. The appendage is closed at its- 
outer end. 

The caecum is the so-called blind portion of the colon 
which extends below the junction with the ileum two or 
three inches. At the entrance of the ileum into the colon is 
a double fold of mucous membrane, within which is a nar- 
row opening; this is the ileo-colic valve. The caecum has. 
openings into the vermiform appendage, the ileum, and 
the ascending colon. The caecum and the vermiform ap- 
pendage are supposed to be rudiments of stomachs found 
in many mammals. 

Structure of the Large Intestine. — The large intestine is 
much like the small intestine. It is surrounded by a cover- 
ing of peritoneum under which lies the muscular coat, con- 
forming in structure to the typical arrangement of longi- 
tudinally and circularly placed fibers. In the circular layer, 
however, at frequent intervals the fibers are lacking, as the 
result of which, the walls being weak, the intestine swells 
out, forming the peculiar baggy appearance of this tube. 
The areolar coat is present and performs the usual function. 



DIGESTION— THE INTESTINES 



nr 



The mucous coat is paler and lighter in color here than in the 
small intestine. It is smooth to the touch, but is thrown 
into many folds and ridges. The large intestine contains no 
villi, but is supplied with certain follicles or glands which 
secrete a mucus that lubricates the walls of the tube. 

The Pancreas. — The pancreas is a compound gland 
similar to the salivary gland in structure and function. It 
lies back of and below the stomach, and extends from left to 
right. It is about six inches long, an inch thick, and red- 



PYLORUS 



DUODENUM 



COMMON 

BILE DUCT 




SUPERIOR MESENTERIC ARTERY 
SUPERIOR MESENTERIC VEIN 



HEAD OF PANCREAS 



Fig. 57.— Pancreas. 

dish yellow, resembling the tongue of the dog both in shape 
and color. The gland is enlarged at the right end where it 
bends downward, occupying a position within the curve of 
the duodenum. 

The lobules, which make up the pancreas, pour their 
contents through small tubes that unite to form a large 
central duct running from the extreme left end of the 
gland. At the right end the duct emerges from the pan- 
creas and enters the duodenum obliquely, in connection 
with the common bile duct. This duct conveys the juice 
secreted by the pancreas and is called the pancreatic duct. 
The pancreas weighs about three ounces. 



IIS 



PHYSIOLOGY AND HYGIENE 



The Liver. — It has already been stated that the upper 
portion of the abdomen is occupied by the stomach and the 
liver, the latter organ lying on the right side. The liver 
is the largest gland in the body, weighing from three to four 
pounds. It is about ten inches long and six inches wide. 
It is smooth on the outer surface and has a reddish-brown 
color. It is divided into two unequal lobes by a fold of 
peritoneum, the right being much the larger, and is of a 



INFERIOR VENA CAVA 
SPIGELIAN LOBE. 




CAUDATE LOBE 
RIGHT LOBE 



LEFT LOBE. 



UrtBlLICAL FISSURE 

PORTAL VEIN. 
QUADRATE LOBE 

GALL-BLADDER, 

Fig-. 58. — Liver. 

loose granular structure, the softer portions being easily 
separated or torn apart. On the under side lying toward 
the back is the gall bladder, and just in front of this is a 
short, deep transverse gash about two inches long called the 
portal fissure. 

The larger portion of the liver is covered with a layer 
of peritoneum, and underneath this is a fibrous connec- 
tive-tissue coat, the real outside coat of the liver, called 
the capsule of Glisson. The small granules, of which the 
liver tissue is composed, are the real liver units or lobules. 



DIGESTION— THE INTESTINES 119 

Histology of the Liver. * — If the portal fissure be ex- 
amined, three tubes will be discovered, running into the 
liver tissue side by side, through a common channel called 
the portal canal. The largest of these tubes is the portal 
vein, the other two are the hepatic artery and the hepatic 
duct. As these three tubes sink deeper into the liver they 
divide and subdivide until small branches of each run in 
between the lobules, from the surface of which they send 
still smaller branches or capillaries into the center. It is in 
the lobules that we find the numerous liver cells which 
secrete the bile and work certain changes in the food to be; 
spoken of later on. 

The blood enters the lobule through the portal vein 
largely, but through the hepatic artery in small quan- 
tities, and then soaks through between the hepatic cells. 
These cells secrete the bile which is cast into the 
hepatic duct through which it is carried out of the liver.. 
The blood is further acted upon by the cells and is then 
taken up by the small capillaries of the hepatic veins.. 
These capillaries unite with others and finally form from 
three to five hepatic veins which pass through the walls of 
the liver, pouring their contents at once into the ascending 
vena cava. 

The Gall Bladder or Cyst. — The location- of this structure 
has already been given. It is a small pear-shaped muscular 
sack or pouch, about four inches long. It serves as a 
reservoir for the excess of bile which is secreted at times 
when it is not needed for digestion. It is composed of 

1 The surplus of albumens " is burned up " or destroyed in the liver. 
As a great amount of combustion takes place at this point much- 
heat is generated and the temperature rises. For this reason the 
liver is probably the warmest portion of the body. 



120 



PHYSIOLOGY AND HYGIENE 



CALL- BLADDER 



CYSTIC DUCT. 



COrtMON BILE-DUCT 



DUODENUM 



three coats. The middle muscular coat by contracting 
serves to eject the bile at the proper time through the cystic 
duct. The latter is a tube about two inches long and 

unites with the hepatic bile 
duct to form the common 
bile duct. 

The common bile duct is 
about the size of a quill and 
is three or four inches long. 
It runs parallel with the 
pancreatic duct for a short 
distance and opens in com- 
mon with the latter through 
an orifice in the walls of 
the duodenum. The walls 
of these tubes have plain 
muscle fibers in them which 
are developed into sphincter 
muscles where they unite 
with each other, the contrac- 
tion of which determines the direction of the flow of the bile. 
Pancreatic Juice. — The pancreatic juice is a clear, 
alkaline liquid, a little heavier than water. It contains 
about ninety per cent of water and a large quantity of 
albumens which coagulate readily upon being heated. The 
important elements, however, are the three ferments, tryp- 
sin, amylopsin, and steapsin. The pancreatic juice is a much 
more active digestive agent than the gastric juice, its great 
activity being due to the action of these ferments. In addi- 
tion to the albumens and ferments there are present a number 
of mineral salts. The ferments cannot act in the presence 
of an acid, hence the pancreatic juice is alkaline in reaction. 




Fig. 59.— Gall bladder. 



DIGESTION— THE INTESTINES 121 

The Bile. — As already indicated the bile is secreted by 
the liver. It is a bitter, greenish-yellow, alkaline secretion, 
somewhat heavier than water and having a peculiar taste 
and odor. It contains about the same per cent of water as 
does the pancreatic juice. In addition it contains small 
quantities of mucin, mineral salts, certain bile salts, and 
traces of soap and fats. 

The Intestinal Juice. — This is secreted by the crypts of 
Lieberkuhn and contains a large per cent of water, some 
albumen, several ferments, and mineral salts. It is yellow 
in color, alkaline in reaction, and slightly heavier than 
water. Its composition and uses have not yet been fully 
worked out. 

Intestinal Digestion. — The pulpy mass of partially 
digested food is sent from the stomach through the pylorus 
into the duodenum as already described. At this point 
it is called chyme. In the duodenum the peristaltic action 
of the intestine mixes the chyme with the pancreatic juice 
and the bile. The three ferments of the pancreatic juice 
immediately attack the food particles, reducing them to a 
liquid condition. The contents of the intestine are alkaline 
as the result of the introduction of the pancreatic and in- 
testinal juices. 

The trypsin continues the work of the pepsin, changing 
the remaining insoluble proteids into soluble peptones. 
The amylopsin supplements the action of the ptyalin 
of the saliva, whose action was arrested by the hydro- 
chloric acid in the stomach. In the small intestine the 
ptyalin and the amylopsin together complete the change 
of the starches into sugar, the latter, however, having the 
greater effect. 

The steapsin breaks a portion of the fats up into fatty 



122 PHYSIOLOGY AND HYGIENE 

acids and glycerin, forming a soluble substance much like 
ordinary soap, hence the term saponification commonly 
applied to this process. This soapy mixture now assists 
in emulsifying the remaining fats. An emulsion consists of 
a solution in which the fats or oils are broken up into very 
small globules or droplets that are suspended in the solu- 
tion. The emulsion of the fats makes it possible for the 
cells of the villi to pick up these small particles or droplets 
and carry them bodily into the lacteals. 

The action of the pancreatic juice is more important 
than that of any other single digestive agent on account 
of its threefold function. The trypsin performs the func- 
tion of the pepsin in digesting the proteids; the amylopsim 
that of the ptyalin in digesting the starches; and the steap- 
sin, that of the bile in emulsifying the fats. 

The action of the bile as a digestive agent is not 
as important as that of the other juices. However, in- 
directly its importance is very great. It assists the steapsin 
in emulsifying the fats and probably stimulates the peri- 
staltic action of the intestine, thus aiding materially in 
mixing the secretions and food particles. Moreover, its 
ferments seem to act as an antiseptic on the contents of 
the intestine, preventing premature putrefaction of the 
same. The principal use of the bile, however, is to carry 
excretions from the body. 

It might be well to say that probably a large portion 
of the valuable material in the bile is reabsorbed by the 
blood vessels and saved to be secreted once more by the 
liver. The intestinal juice probably affects the starches 
slightly and changes the sugars into compounds that are 
more readily absorbed. During intestinal digestion the 
food is reduced to a thick milky solution called chyle which 




Fig. 60.— Diagram of digestive apparatus. 

mouth; 6, stomach (thickness of walls exaggerated); c, small intestine; d, large 
intestine; e, liver; /, pancreas; g, common bile duct; h, pancreatic duct; i, gall 
bladder from which passes the cystic duct; j, k, gastric and mesenteric veins 
which unite to form the portal vein; /, hepatic vein; m, ascending vena cava; 
n, left subclavian vein; o, thoracic duct; p, receptaculum chyli; r, lacteals; s, villi; 
/, caecum; x, salivary glands; y, gastric glands; z, intestinal glands. 

123 



124 PHYSIOLOGY AND HYGIENE 

is now ready for absorption. The waste or indigestible 
material is carried on into the large intestine and finally 
ejected from the body. 

Review of Digestion. 1 — The food is taken into the mouth 
and thoroughly masticated, being subjected to the action 
of the alkaline saliva, the ptyalin of which changes some of 
the starches into sugar. 

The mixed and partially digested food is now swal- 
lowed and cast into the stomach, which continues the 
mixing process by means of its peristalsis. Here the con- 
tents are rendered acid by the hydrochloric acid, which 
also dissolves the mineral matter intended for food. The 
pepsin changes some of the proteids into soluble peptones, 
and the rennet curdles milk. The starches and fats are not 
affected. However, the fats may have their albuminous 
coverings digested off by the pepsin. 

The pulpy mass now called chyme is ejected through 
the pylorus into the duodenum, where the peristalsis of 
the intestine mixes it with the three alkaline digestive 
agents introduced here. The trypsin of the pancreatic 
juice digests the proteids not affected by the pepsin; the 
amylopsin and the ptyalin of the saliva act on the starches, 
changing them to sugar; while the steapsin breaks up or 
emulsifies the fats. The bile acts as an antiseptic on the 

1 Not all animals chew their food when it is first taken into the 
mouth. The cow spends the day in gathering food into her ca- 
pacious stomach and at night while she is resting she belches 
small wads of grass or hay up into the mouth and chews them. 
The food is then swallowed again and sent into another compart- 
ment where it is further digested. Many persons have an old- 
fashioned idea that a cow has a real cud, and if she loses it she will 
die. This is not true. The cud is the ball of grass which is being 
chewed at the cow's leisure. 



DIGESTION— THE INTESTINES 



125 



CAPILLARIES 



ARTERY 



contents of the intestine and assists in emulsifying the 
fats. The intestinal juice probably affects the starches 
and sugars. 

Alcohol and Digestion. — Alcohol seriously affects the 
mucous membrane of the stomach and intestines, produ- 
cing inflammation of 
the same. In time, 
congestion of this 
membrane appears, 
and if the practice 
of drinking alcoholic 
beverages be con- 
tinued long enough 
the congestion in the 
stomach gives way 
to great red blotches 
or ulcerations. It 
is evident that in 
a diseased stomach 
of this kind the 
proper secretion of 
the gastric juice is 
impossible and in- 
digestion is the re- 
sult. 

Tobacco and Digestion. — The action of alcohol and 
tobacco on delicate membranes is much the same. Inas- 
much as tobacco hardens these tissues, it prevents the 
secretion of the various juices and leads to dyspepsia. 




Fig. 61. 



'Enlarged view of a villus, 
showing parts. 



CHAPTER XVI 

ABSORPTION 

Absorption. — We have just learned how the food taken 
into the mouth is so changed by the different digestive fluids 
and reduced to such a soluble condition that it is now ready 
to be taken up by the blood and sent out over the body to 
nourish the tissues of the same. The process by means 
of which the digested food material is transferred from 
the alimentary canal into the blood and lymph is called 
absorption. 

To the student of chemistry the changes that take 
place in digestion are not altogether mysterious, as the most 
of these changes have been worked out in the laboratory. 
However, the process of absorption is not so easily under- 
stood. It is well known that a large part of the food 
elements get through the walls of the villi by a familiar 
physical process known as osmosis. 

But not all the material is transferred in this way. 
Even dead membranes will permit of osmosis of soluble 
substances, but it is impossible for insoluble portions, 
such as the small droplets of fat, to be carried through 
in this way. Careful investigation on the part of scientists 
has proved that the living cells are directly instrumental 
in transferring these substances through the walls of the 
villi. 

Osmosis. — Osmosis is the process by which liquids tend 
to pass through porous membranes. If a solution of blue 

126 



ABSORPTION 127 

vitriol be separated from water by a sheet of parchment 
paper and permitted to stand for some time it will be ob- 
served that the water gradually takes on a bluish tinge, 
showing that some of the blue vitriol has passed through 
the parchment paper into the water. It can also be 
shown that some of the water has passed through into the 
blue vitriol. 

This mixing of liquids of different densities is osmosis. 
While liquids are mixed in this way through dead 
animal membranes, the process is probably carried on 
more rapidly through living animal tissues. A large por- 
tion of the liquid food in the intestine . gets into the blood 
through the walls of the villi by osmosis. 

Active Influence of the Cells. — It has already been stated 
that the emulsified fats cannot be passed through the w T alls 
of the villi by the simple process of osmosis. Careful in- 
vestigation shows that the epithelial cells covering the villi 
take up the small particles of fat that come in contact with 
the cell walls, pass them through their bodies, and discharge 
them into the lacteals on the other side. Moreover, the 
white blood corpuscles may be seen moving between the 
epithelial cells, wrapping their bodies about the fat drop- 
lets and carrying them through to the lacteals. Scientists 
now agree that absorption is due in part to the active 
agency of the living cells. 

Absorption in the Mouth. — Physiologists are not agreed 
in regard to absorption in the mouth. Some think that 
water and sugar are absorbed here in small quantities. In 
any event the amount of food material absorbed at this 
point is so small as to be of no physiological value. 

Absorption in the Stomach. — Previous discussion has 
shown that the use of the stomach as a digestive organ is 



128 PHYSIOLOGY AND HYGIENE 

unimportant when compared with that of the small intes- 
tine. Its use as an absorbing agent is still less important. 
Its chief function seems to be that of a receptacle where 
the food is held for some time and thoroughly churned 
up by the peristalsis of the stomach. It is possible 
that small quantities of sugars, peptones, and water are 
absorbed in the stomach and thrown into the gastric 
vein. Traces of mineral salts may also be absorbed in 
the stomach. 

Absorption in the Small Intestine. — It is in the small 
intestine that the larger portion of foodstuffs is absorbed. 
It has already been shown that the inner surface of the small 
intestine is covered with numerous minute projections called 
villi. From the description of these little organs we learned 
that they are covered with a single layer of epithelial cells 
and contain plain muscle fibers, nerves, lacteals, and small 
blood tubes, which are the beginning of the branches of the 
mesenteric vein. The veins and lacteals lie very close to 
the layer of epithelial cells. 

The villi are the true organs of absorption, and we can 
see how it is only necessary for the food material to pass 
through the cells of the epithelium to get into the blood 
or lymph. As previously explained, the soluble material 
passes through at once by the simple process of osmosis. 
The sugars changed by the ferments are now passed through 
the cells and cast into the mesenteric vein. The proteids, 
as soluble peptones, are transferred at the same time and 
thrown into the mesenteric vein. The water and mineral 
salts are absorbed in the same way and cast into the same 
vein. Likewise the fats which have been saponified are 
absorbed, but are thrown into the lacteals instead of the 
mesenteric vein. 



ABSORPTION 129 

It has already been stated that the fine droplets in the 
emulsified fats are absorbed by the living cells, carried 
through the same, and dropped into the lacteals, or else 
they are picked up by the white blood corpuscles, which 
wander in between the epithelial cells, and conveyed by 
them to the lacteals. 

Changes Occurring During Absorption. — We eat proteid 
food in the form of legumin, myosin, casein, or gluten, and 
fats in the form of tallow, butter, lard, or oil, and finally 
find these different kinds of proteids and hydrocarbons 
built into the body as human albumen or human fat. The 
question very naturally arises as to how and where these 
different kinds of albumens and fats are changed into 
human albumens and fats. 

A careful study on the part of scientists reveals the 
fact that the soluble peptones are absorbed as such, but 
appear in the blood immediately after absorption as hu- 
man albumen. Nature has probably provided for this 
change for two reasons : in the first place, a peptone acts 
as a mild poison when injected into the blood as a pep- 
tone, hence it must be changed into the albumen form as 
quickly as possible'. 

Moreover, the soluble peptone, after once being absorbed, 
might just as easily pass back into the intestine were it 
not for the fact that it is changed to the insoluble human 
albumen as it is dropped into the blood, thus preventing 
its return to the intestine. 

The fats also are changed from the form in which they 
appear in the intestine into human fat. This change like- 
wise takes place as the fat particles are passed through the 
cells, and is probably affected by the action of the cells 
themselves. 



J30 PHYSIOLOGY AND HYGIENE 

Alcohol and Absorption. — Inasmuch as alcohol hardens 
'the delicate walls of the minute villi they can no longer 
perform the function of absorption properly; and even 
though the food is fully digested, it cannot get into the 
blood. 



CHAPTER XVn 

METABOLISM 

Metabolism. — Metabolism is the process by means of 
which nutritive material is taken up by the living cells, 
and as a result of which the cells are broken down and dis- 
integrated into simpler substances. The building-up proc- 
ess by which the nourishment is taken in by a worn-out cell 
to reconstruct its body or in which the food material is 
worked into new cells, is called anabolism or assimilation. 
The destructive process by which the living cells are torn 
down into simpler compounds is called catabolism. Me- 
tabolism, then, includes the two processes of assimilation 
or anabolism, and catabolism. 

Assimilation. — We have observed how the food ele- 
ments have been thrown into the blood; it will be of interest 
now for us to trace each of the foodstuffs and determine 
where and how it becomes a part of the living body. 

Proteids or Albumens. — On another page we learned 
that the soluble peptones are cast into the blood as the re- 
sult of absorption. The gastric veins from the stomach and 
the mesenteric veins from the intestine receive the albumens 
and carry them to the large portal vein, which conveys them 
to the liver. A sufficient amount of albumens is carried 
at once through the liver into the general circulation to 
keep the supply in the blood up to the required amount. 

From the blood these albumens are built into absolutely 
new cells where new ones are being formed. Where an 

131 



132 PHYSIOLOGY AND HYGIENE 

old cell has been torn down the non-nitrogenous part of the 
albumen is used to rebuild the cell. The nitrogenous part 
then appears as waste matter and is eliminated from the 
body. 

It is seen, then, that albumens are required only when 
new tissue is being formed, as in the case of growing chil- 
dren. At any other time the albumen must be broken up 
before it can be used, and then a portion of it must be 
excreted. If too much proteid food has been taken into 
the body, the excess of albumen is broken down in the 
liver. It is either decomposed into a fat and a nitroge- 
nous portion or a sugar and a nitrogenous portion. In 
either case the nitrogenous part appears as a solid sub- 
stance known as urea, and is excreted as such. The fats 
and sugars formed are assimilated, as are any other fats 
or sugars taken into the body. 

Sugars. — The sugars are absorbed and carried by the 
portal vein to the liver, where the excess is stored up in the 
liver tissue as an insoluble liver starch called glycogen. 
Were it not changed to the insoluble form it could not be 
stored up. As the sugar is needed throughout the body the 
glycogen is changed back into the soluble sugar, which is 
carried by the blood to torn-down tissue where it unites 
with the nitrogenous portion of the old cell to rebuild the 
same. No provision is made by nature for storing up sugar 
as such in any part of the body. It must be used in build- 
ing up old tissue or else stored up as glycogen. 

Fats or Hydrocarbons. — The fats are not taken up by the 
blood, but are cast into the lacteals which carry them to the 
receptaculum chyli. From this point they are carried by 
the thoracic duct to the left subclavian vein, where they 
are thrown into the blood. Whatever fats are needed by 



METABOLISM 133 

the tissues are carried to worn-out cells and assimilated as 
in the case of the sugars. 

While the excess of sugars is stored up in the liver as 
insoluble glycogen, the excess of fats is carried to various 
parts of the body and deposited in the tissue as small fat 
droplets. ■ Large quantities are stored in the areolar tissue 
under the skin, forming adipose tissue. This deposit of 
fat gives the roundness and plumpness to the body of 
children and some older people. As the system demands 
the fat it is taken up by the blood and carried to the 
point where it is needed. 

Some animals store up great quantities of fat during the 
summer and use the same during the long winter months. 
The bear is quite fat in the fall of the year, but very 
lean in the spring. 1 

Mineral Salts. — Salts are used in the formation of new 
tissue and the repair of old. The salts are absorbed and cast 
into the blood which carries them to all parts of the body, 
where they are assimilated by bone, the red corpuscles 
of the blood, and the brain, as well as other structures. 

Water. — Water is absorbed all along the alimentary 
canal, but its chief use is to act as a solvent of the various 
substances in the body. 

Catabolism. — After the food elements have been as- 
similated and built into the structure of the body there 

1 A few animals during the summer time accumulate a large quan- 
tity of adipose tissue beneath the skin. As a result they grow 
fat and lazy by autumn, and when cold weather approaches retire 
to their dens, where they sleep away the long winter months. Dur- 
ing this time the excess of fat is used up in sustaining the body, 
and the animal comes out in the spring thin in flesh and ravenously 
hungry. Animals that store up fat in this way and then retire for 
the winter are called hibernating animals. The bear is a good 
illustration of a hibernating animal. 



134 PHYSIOLOGY AND HYGIENE 

would be no necessity for more food were it not for the fact 
that the tissues of the body are constantly being worn out 
and torn down, the waste matter being carried away. 

Neither heat nor energy would be liberated were it not 
for the fact that the cells of the body are continually being 
burned away, so to speak. To secure heat and energy in the 
case of the steam engine, coal is burned under the boiler 
in the presence of oxygen. The combustion of the coal 
furnishes heat to the water, which is changed into steam, 
which, in turn, furnishes the energy necessary to run the 
engine. In the combustion of the coal there is left behind 
ashes in the ash pit, and smoke and carbon dioxide escape 
through the flue. 

When combustion takes place in the tissues of the body 
the cell unites with oxj^gen from the blood forming the 
nitrogenous compound already mentioned, water, and car- 
bon dioxide. * The nitrogenous compound is usually retained 
to be built up in the structure of the repaired cell, but it 
sometimes becomes unfit for further use and is cast off as 
waste matter. The water and carbon dioxide are sent to 
the organs of excretion, through which they are eliminated 
from the body in a manner to be described later. 

Review of Digestion, Absorption, and Assimilation. — The 
food is taken into the mouth, where it is thoroughly masti- 
cated and reduced to a pulpy mass by means of the teeth, 
tongue, and cheeks. Rolled into small pellets or masses it 
goes through the process of deglutition or swallowing by 
means of which it is carried to the stomach. The peristalsis 
of the stomach churns the food up and, assisted by the action 
of the gastric juice, reduces it to a semi-liquid material 
called chyme. When this condition is reached the pylorus 

1 This process is called oxidation. 



METABOLISM 135 

opens and the chyme is cast into the small intestine. Here 
the slow, peristal tic action of the intestine keeps the con- 
tents moving while the pancreatic juice, the bile, and the 
intestinal juice perform their functions. While small 
quantities of foodstuffs are absorbed by the blood vessels 
in the stomach, the greater portion is absorbed by the villi 
of the small intestine. 

Proteids. — The insoluble proteids are not digested in the 
mouth, but are acted upon by the pepsin of the gastric 
juice in the stomach, where they are changed into soluble 
peptones. The. trypsin of the pancreatic juice in the small 
intestine completes the process begun by the pepsin of 
changing the proteids into peptones. The peptones are 
now absorbed by the villi and cast into the mesenteric vein, 
being changed into insoluble human albumen during the 
process of absorption. From the mesenteric vein they are 
carried to the portal vein, through which they are conveyed 
to the liver. In the liver the excess of albumen is broken 
down into sugar and a nitrogenous compound or fat and a 
nitrogenous compound. A sufficient amount of albumen is 
carried through the liver to keep the proportion of the same 
up to a required amount and to furnish the necessary 
material for the building up of absolutely new tissue. 

Fats or Hydrocarbons. — The fats are not digested in 
either the mouth or the stomach, although the pepsin may 
dissolve their albuminous coverings off in the latter organ. 
In the small intestine the fats are digested and emulsified by 
the steapsin of the pancreatic juice and the bile. Being 
absorbed by the villi, the fats are taken up by the lacteals, 
carried to the receptaculum chyli, and conveyed by the 
thoracic duct to the left subclavian vein, where they are 
cast into the blood. 



136 PHYSIOLOGY AND HYGIENE 

Wherever they are needed they at once unite with the 
nitrogenous portion of a broken-down cell to rebuild the 
same. The excess of fats is stored in various parts of the 
body as adipose tissue; later, when needed, this fat is picked 
up by the blood and used as before. 

Sugar and Starches or Carbohydrates. — The carbo- 
hydrates are acted upon in the mouth by the ptyalin, which 
changes the starches to sugars, but are not digested in the 
stomach. The amylopsin of the pancreatic juice completes 
the digestion of the carbohydrates rendering them soluble. 
Being absorbed by the villi they are sent by the portal cir- 
culation to the liver, where the excess is stored up as in- 
soluble liver starch, called glycogen. A portion is carried 
through the liver by the blood and used, as were the fats, 
in repairing old worn-out cells. When needed, the glycogen 
is changed back into sugar and used as before. 

Mineral Salts. — The salts are rendered soluble by the 
hydrochloric acid in the stomach and are probably absorbed 
in the small intestine, from whence they are carried by the 
blood through the liver and assimilated by the tissues 
needing them. 

Water. — Water is not acted upon by any of the digestive 
agents and is absorbed all along the alimentary canaL 



CHAPTER XVIII 

FOODS 

We have just completed an extended study of digestion, 
absorption, assimilation, and catabolism. In this study we 
learned that the cells of the body are built up from and 
repaired by certain material prepared for this purpose. 
We shall now enter upon a discussion of the source, 
composition, and value of the different substances that, 
taken into the body, finally enter into its structure. 

Foods. — To maintain the supply of material necessaiy 
to build up and repair the tissues of the body from eight to 
ten pounds of food are consumed daily. The question may 
arise in this connection as to what constitutes food. Not 
everything taken into the body is a food. To be such, a 
substance must contain elements that may be worked 
over into living tissue. Foods, then, are substances which 
furnish material from which the tissues of the body may 
be constructed and from which the body may derive 
the energy necessary for its activity and motion. Con- 
sequently, any of the numerous nutritive substances that 
appear daily on our tables may be considered foods. 

Foodstuffs. — It would be a difficult task to classify and 
discuss singly all of the many foods with which we are 
familiar. While the number is very large, the nutritious 
elements which they contain are comparatively few. 
These elements are variously known as proximate princi- 
ples, alimentary principles, or foodstuffs. They include (1) 

137 



138 



PHYSIOLOGY AND HYGIENE 



proteids, (2) albuminoids, (3) carbohydrates, (4) hydro- 
carbons, and (5) mineral salts. Water is sometimes in- 
cluded among the foodstuffs. We have already learned 
something of the digestion and assimilation of these ele- 
ments. We shall now give them a little more consideration. 

Proteids. — This class of foodstuffs is composed of carbon, 
hydrogen, oxygen, nitrogen, and traces of other elements. 
Inasmuch as the proteids contain large quantities of nitro- 
gen from which the supply for the tissues of the body is 
obtained, they are sometimes called nitrogenous foods. 
They are more frequently called albumens. The proteids or 
albumens are found in a large variety of foods. In lean 
meat, the proteid is known as myosin; in the white of egg, 
egg albumen; in cheese and milk, casein; in grains and 
cereals, gluten; in peas and beans, legumin; in blood, fibrin. 
While these different foods are very much unlike, the pro- 
teid elements in each is practically the same as that in all 
of the others. 

Albuminoids. — The albuminoids are really representa- 
tives of the albumens, inasmuch as they are composed of 
carbon, hydrogen, oxygen, and nitrogen. There is this 
difference, however: the nitrogen of the proteids enters 
into the structure of a large part of the albuminous tissues 
of the body, while the albuminoids do not seem to furnish 
any large amount of nitrogen to these tissues. The only 
important food containing albuminoids is gelatine. 

Carbohydrates. — The carbohydrates are composed of 
carbon, hydrogen, and oxygen, the last two being present 
in the proportion to form water. This fact may be proved 
by placing one of the carbohydrates on a hot stove, when 
the water will be driven off, leaving the black carbon 
behind. This class of foodstuffs includes the sugars and 



FOODS 



139 



starches. These are the main source of heat and muscular 
energy, form the bulk of our food, and are the most easily 
digested and cheapest of all foods. 

Hydrocarbons. — The hydrocarbons are composed largely 
of carbon and hydrogen and include the fats and oils. The 
difference between a fat and an oil is in the consistency 
rather than in the composition. The hydrocarbon is called 
a fat when it is in a solid condition and an oil when in a 
liquid form. Butter is 
a fat when hard and an 
oil when melted. 

The principal fat foods 
are: butter, lard, and 
tallow. The oils are 
usually of vegetable ori- 
gin, as cotton-seed oil, a 
substance which has re- 
cently come into promi- 
nence as a valuable 
food. The hydrocarbons 
produce a large amount 
of energy, hence they are of great value in cold regions. 
In warm climates, however, they should be used to sup- 
plement the carbohydrates. Since the hydrocarbons and 
carbohydrates contain no nitrogen they were formerly 
called non-nitrogenous or carbonaceous foods. 

Mineral Salts. — These salts are composed largely of 
phosphate of lime, carbonate of lime, and common salt. 
Traces of other salts are taken into the alimentary canal and 
finally built into the system. Mineral salts are found in con- 
siderable quantities in bone, cartilage, the brain, and else- 
where. About sixty-five per cent of bone is mineral matter. 




Fig*. 62. — An Herbivorous Animal. 



140 



PHYSIOLOGY AND HY(TlENE 



Kinds of Foods. — As already suggested there are many 
kinds of foods. The different tastes of individuals have 

developed a large 
variety of palatable 
viands for our tables, 
containing the vari- 
ous foodstuffs in 
proportions to suit 
the needs of each 
and every person. 
A few of the com- 
mon foods from 
which we draw a 
nourishment will be 




Fig-. 63.— A Carnivorous Animal. 



large part of the material for our 
briefly discussed here. 

Origin of Foods. — The supply from which our food is 
obtained comes primarily from the soil and air. The rocks 
about us disintegrate, producing a finely divided material 
which is acted upon chemically by atmospheric and other 
agencies until it is changed into our familiar soils. Vege- 
tation springs up on these soils, building up different soil 
elements, with the carbon dioxide of the air, into corn and 
wheat and potatoes and scores of other vegetable products 
fit for use as food for animal life. Not all animals, how- 
ever, subsist upon vegetation alone. While some animals, 
such as cattle, sheep, and horses, live almost entirely 
upon vegetation, there are others, such as the lion and 
tiger in their wild state, that depend entirely upon other 
animal life for their supply of food. 

The animals in the first class are called herbivorous, those 
in the second class, carnivorous animals. There are some 
animals, however, that belong to both classes, eating both 



FOODS 



141 



vegetation and flesh; these are called omnivorous animals. 
Man is omnivorous, eating food from both vegetable and 
animal sources. 

We shall observe, then, that the function of vegetable 
life is to organize the food elements found in the soil into 
substances that may be digested by the organs associated 
with the alimentary canal. When taken into the body of 
the animal these substances ere still more highly organized ; 
as a result of this second change they contain, in general, a 




Fig-. 64. —Dogs are both Carnivorous and Herbivorous. 

greater per cent of material that may be actually worked 
over into the tissues of the body. In discussing the kinds 
of food, those that are derived directly from vegetable 
sources will be treated of first. 

Bread. — This is a general term applied to a class of 
food made from the meal of wheat, corn, rye, potatoes, 
beans, chestnuts, etc. Ordinarily, however, it includes 
only those rolls, cakes, loaves, or biscuits made from the 
flour or meal of wheat, barley, rye, or corn. Bread is one 
of the most common and substantial foods used by man. 



142 PHYSIOLOGY AND HYGIENE 

Wheat bread, especially, is common among all classes of 
people in civilized lands. Its value is enhanced by its ap- 
pearance and agreeable flavor. It contains from fifty-five 
to sixty per cent of carbohydrates and five to eight per cent 
of fats. Since the carbohydrates take such a leading part in 
the repair of the body, wheat bread is a highly desirable food. 

Rye bread contains a lesser amount of each of these two 
foodstuffs, with a greater quantity of water, hence its 
nutritive value is not so great. 

Corn bread contains less carbohydrates and more hydro- 
carbons, but, as both of these foodstuffs are necessary for 
building up torn-down tissue, corn bread must be ranked 
as a valuable food. Corn bread and rye bread are fre- 
quently preferred above wheat bread on account of the 
fact that the meal is coarser and seems to have a stimu- 
lative effect upon the walls of the alimentary canal, pro- 
ducing a greater flow of the digestive fluids. Then, too, 
the bran or hull of the grain is usually left in the meal and 
furnishes a supply of other foodstuffs, such as the phosphates, 
which are lacking in the white wheat bread. Where the 
whole of the wheat is used in making brown bread we have 
all of the elements and all of the good qualities of the rye 
and corn bread. 

Potatoes. — Potatoes are among the staple articles of 
food. Their culture has a wide range and it costs but little 
to raise them. About seventy-five per cent of the potato 
is water, and twenty per cent carbohydrates, with a small 
quantity of proteids. The value of the potato, however, 
is due almost altogether to its supply of carbohydrates. 
It is true that a large quantity of water must be taken into 
the system in order to obtain the starch, but, inasmuch 
as water is necessary also, this is not objectionable. 



FOODS 143 

Wherever they may be obtained, potatoes are used in 
large quantities by all classes of people. It is to the poorer 
classes, however, that potatoes are especially valuable. 
On account of their cheapness they can be purchased 
by those of moderate means and prepared for the table 
in ways that are both appetizing and economical. Even 
though the only foodstuff of any importance in the potato 
is starch, yet it must be ranked high as an article of food. 

Rice. — A food that has come into quite general use 
throughout the civilized world is rice. Raised on soil that 
will ordinarily not support other kinds of crops, rice is pro- 
duced cheaply and in great quantities. It differs from the 
potato in that it can be shipped to all parts of the world and 
preserved for an indefinite period of time. It is much richer 
than the potato in foodstuffs, containing about seventy- 
five per cent of carbohydrates, ten per cent of proteids, the 
remaining portion being made up largely of water. Rice 
may be prepared for the table in a variety of ways. This 
fact, combined with its cheapness and nutritive qualities, 
makes it a valuable food for all classes of people. 

Peas and Beans. — The leguminous plant produces seeds 
that are especially rich in the proteid, legumin. Many of 
the wild varieties, such as the buffalo pea and the buffalo 
bean, have been utilized as food. The common forms 
found in our gardens are the pea and the bean. Both of 
these furnish substantial foods over large sections of the 
country. Both are cooked while still green, although the 
bean is used in the ripened form at all seasons of the 
year. Each contains about fifty per cent of carbohydrates, 
twenty-five per cent of proteids, and two per cent of fats, 
the remaining portion being made up of water and non- 
nutritive material. Peas and beans represent a high type 



144 PHYSIOLOGY AND HYGIENE 

of foods inasmuch as they are so nutritive and can be raised 
so easily. 

Macaroni. — Another food similar to rice in composition 
is macaroni. This is a material originally manufactured in 
Italy, but lately it has been produced in other places. It 
is made from a special kind of very hard, transparent 
wheat. The wheat is usually ground into a flour, made 
into a paste, and rolled into slender tubes. On account of 
its shape it is sometimes called vermicelli. Its use has 
increased rapidly in recent years, but it will hardly become 
as popular a food as rice. It contains about the same 
proportion of foodstuffs as does rice. 

Turnips. — The small proportion of food elements found 
in turnips places them low in the order of nutritious foods. 
They contain over ninety per cent of water, the rest being 
largely carbohydrates. By many, however, they are con- 
sidered both refreshing and nutritious when eaten raw. 
Many people are fond of them when they are cooked and 
placed on the table. They do not rank high as a tissue 
builder. 

Fruits. — Fresh fruits contain but little more nutritive 
food elements than turnips. They have a certain value, 
however, that makes them especially desirable as foods. 
Eaten in the summer time when large quantities of water are 
cast off through the perspiration, fresh fruits are very re- 
freshing. Moreover, the fruit acids and flavors tend to 
stimulate the appetite and to produce a greater flow of 
the digestive juices. Even the sight of richly colored, 
ripened fruit on the table will make the " mouth water." 
What is more appetizing on a warm summer evening than 
a great clump of dark luscious grapes or a dish of yellow- 
ish, red-cheeked peaches? 



FOODS 145 

In addition, fresh fruits have a nutritive value that is 
not to be underestimated, especially in a warm climate, 
where a dietary of sugars and starches is so necessary. 
The average fresh fruit contains no less than ten per cent 
of carbohydrates in addition to a very small quantity of 
proteids. 

Dried fruits, while not so desirable in many respects, con- 
tain a greater per cent of food elements than fresh fruits. 
In most dried fruits the proportion of foodstuffs runs up to 
fifty per cent, the larger part of which is sugar. The dried 
fruits may be transported to distant sections of the land 
without spoiling and may be used at all times of the year. 

Foods Derived from Animal Sources. — In the discussion 
just given on vegetable foods it may have been observed 
that they are especially rich in the sugars and starches. It 
is true that in the peas and beans, as well as in some of the 
cereals, there is a great quantity of proteids, yet it is to the 
meats of various kinds that we must look for our substantial 
supply of these foodstuffs as well as the hydrocarbons. 

In the selection of foods, not only the quantity of food- 
stuffs, but the matter of digestibility as well, should be 
considered. If we compare the relative digestibilities of 
vegetable and animal foods we shall find that the former 
are more difficult to digest than the latter. 

It has already been suggested that the function of plant 
life is to build up organized matter as food for animal life. 
While animal foods are usually more easily digested than 
are the vegetable, it does not always follow that they are 
more desirable. An excess of nitrogenous, or proteid, 
foods in the system frequently gives rise to disorders that 
materially affect the health of the body. The relative values 
of a few of the common meats will now be considered. 



146 PHYSIOLOGY AND HYGIENE 

Beef. — The vast herds of cattle that cover our hills and 
plains show the popularity of beef as a food. Lean meat 
of the beef is rich in the albumen, myosin, already men- 
tioned under the subject of foodstuffs. In different forms 
it constitutes one of the standard foods of both rich and 
poor. 

Beefsteak is especially nourishing, but should be carefully 
cooked. If fried hard it can be digested easily only by 
laboring men. In the rare condition it resists the action 
of the digestive agents less and permits a greater portion 
of its elements to be absorbed. Tough beefsteak can be 
more easily chewed after having been thoroughly pounded. 
Steak so tough that it cannot be masticated fully should be 
discarded. 

Roast beef is a desirable food, but it should be remem- 
bered that an excess taken into the body gives rise to 
serious disorders, inasmuch as it must be broken down 
into a nitrogenous product, the elimination of which over- 
works the organs of excretion. A dietary should be pro- 
vided. The fats in beef make it more palatable and at 
the same time render it more nourishing. 

Pork. — -While there is a prejudice among some people 
against the hog, it cannot be denied that its meat is an 
important food. What has been said of the value of beef 
can be repeated here concerning pork. It is considered, 
however, less digestible than beef. Prepared in the form 
of sausage, it gives a food that is relished by many. Its 
large quantity of fat furnishes a great amount of heat and 
energy. Pork is both cheap and nourishing, but like beef 
it should not be used in excess. 

Mutton. — The flesh of sheep has long been considered 
a delicacy by many persons. It contains both fat and 



FOODS 147 

albumen. Although mutton has in it those elements that 
are necessary to the body, it hardly ranks with pork and 
beef as a food. However, if alternated in our dietaries 
with these, it furnishes a change that is beneficial to both 
taste and body. 

Fowls. — From the very beginning, fowls of different 
kinds have been popular as food producers. The common 
barn fowl supplies us with tender, attractive meats that 
are unrivaled. Fried chicken is one of the delicacies of 
the season. For easy digestion and nourishment, stewed 
chicken cannot be surpassed. It hardly needs to be men- 
tioned that turkey is a prime favorite. What boy has not 
anticipated, days in advance, the large, plump, dripping 
body of the Thanksgiving turkey? Wild game, such as 
duck, geese, quail, prairie chicken, etc., is desirable in 
season. The gravy from the meat of fowls is exceedingly 
delicious and nourishing. 

Fish. — The flesh of fish gives a pleasing variety in our 
dietaries. While perhaps not such an important muscle 
builder as other kinds of meats, yet fish has a value all its 
own. Fish flesh contains a relatively large quantity of 
mineral substances, particularly phosphates. Since the 
brain requires a certain supply of phosphorus for its normal 
development, it is readily seen that fish makes a splendid 
brain food. 

Salmon is both palatable and nourishing. The large 
quantity of soft bones included in its flesh supplies the 
mineral matter so necessary to the growth of bone. Salmon 
is also a brain food. Caution should be observed in the 
matter of choice of fish in the market. Fish flesh rapidly 
decomposes, as a result of which certain poisons are de- 
veloped that are serious in their effect. 



148 PHYSIOLOGY AND HYGIENE 

Eggs. — A standard animal product is the egg. The 
white of the egg is composed largely of albumen, while the 
yellow is made up of fat. For breakfast nothing surpasses 
eggs and toast or eggs and ham. The egg is valuable not 
only as a food, considered as such, but also on account of 
its many uses in connection with other forms of food. The 
supply of many kinds of produce may be shut off, but the 
housewife is well-nigh in despair when eggs fail to find their 
way into the kitchen. Its high nutritive value, together 
with its wide range of production, makes of the egg a 
universally popular food. 

Milk. — Rivaling the egg, both in nutrition and popu- 
larity, the milk of the cow is used by all classes of people. 
Milk is the natural food of the young of all mammals. In- 
asmuch as it will alone support life for long periods of time, 
it is evident that it contains all of the elements necessary 
to the building up of animal tissues. 

Analysis of milk shows this to be true. In milk are 
found the proteid, casein, milk sugar, fats, mineral salts, and 
water. It will thus be observed that it is an ideal food, 
especially for children. Like eggs, it is used alone, or in 
the preparation of many other forms of food. It should 
be kept clean and pure so that poisonous elements may 
not develop in it. The addition of chemicals to prevent 
souring is to be condemned. If one suspects that milk 
has been treated in this way, a careful examination ought 
to be made by the proper authorities. Only pure, sweet, 
unadulterated milk should be used for any food purpose. 

Butter. — The fat of milk, when gathered into a sep- 
arate mass, is called butter. It is a standard food and is 
really one of the necessities of civilization. Being a fat it is 
a powerful heat and energy producer. It is hardly ever 



FOODS 149 

used alone, but is spread on bread, waffles, pancakes, etc. 
It is required in the preparation of many kinds of foods. 
Besides being a necessity, it is a delicacy that aids materially 
in making other forms of food palatable. After standing 
for some time, especially in warm weather, butter becomes 
"old tasted" or rancid. 

Cheese. — Another important product of milk is cheese. 
It is composed largely of proteids, fats, and water. On 
account of its composition it is very nourishing. It is 
usually considered hard to digest. Inasmuch as it is rich 
in food elements it should not be eaten in very large 
quantities. 

Cream. — This is composed of the upper layer of milk 
which includes an excess of fat globules. Cream gathers 
after the milk stands for some time and is then skimmed off. 
It is rich in hydrocarbons and is used with coffee, tea, and 
other drinks to make them more palatable. 

Soups. — In cooking meats much of the nutritive matter 
separates itself from the main portions and, being washed 
out with water, forms soups. Much of this nutritious 
material is already soluble, and for this reason soups are 
especially valuable for the sick and for the convalescing. 
The food taken in this way is more dilute than that taken 
in other forms. Soups are nourishing to those whose 
digestive organs are weak and hence unable to digest the 
foods taken in a more concentrated form. Beef tea con- 
stitutes a very inviting dish to invalids who are recovering 
from some serious disease, particularly of the alimentary 
canal. The warm, nourishing liquid bathes the weakened 
walls of the tubes slightly stimulating the flow of di- 
gestive juices and supplying the nutrition in the proper 
quantities. 



CHAPTER XIX 

RESPIRATION 

Relation Between the Air and the Blood. — It has been 
shown that one of the important functions of the blood is 
to convey the oxygen of the air to the cells of the body and 
to eliminate waste matter from the same. To do this it is 
necessary that the air and the blood be brought into very 
close relation at some convenient point in the progress of 
the latter. 

Upon first thought it appears that some arrangement 
might have been made whereby the blood could be sent 
to the surface of the body and brought in contact with the 
oxygen of the air through the skin. Indeed, an arrange- 
ment quite similar to this is observed in the case of some 
of the lower animals. 1 It is obvious ; however, that the 
skin of man is too thick to permit a perfect interchange 
between the air and the blood. Were the small, delicate 
capillaries through which the exchange of gases takes 
place, spread over the body, they would be subjected to 
injury from both atmospheric changes and mechanical 
agencies. 

1 We are all familiar with the location and arrangement of the 
gills of a fish. These are covered with a thin membrane that contains 
many small blood vessels. Quite a little oxygen is dissolved in the 
water, and as the fish draws this through its gills the oxygen passes 
through the thin membrane walls and gets into the blood. Insects 
have several small tubes entering their body, through which the 
oxygen of the air passes and gets into the liquid which answers the 
purpose of the blood. 

1Z0 



RESPIRATION 



151 



EPIGLOTTIS 



LARYNX 



Nature provided a happy means of exchange by locating 
special organs, the lungs, within the chest where they are 
not liable to injury from without. By means of the lungs, 
the mouth, and the trachea, under the influence of certain 
muscular organs to be described later, the process of respira- 
tion is carried on. To understand this process fully, we 
must study the structure of these organs and their relation 
to each other. 

The Larynx. — The larynx connects with the pharynx 
above and is continued into the trachea or windpipe below. 
It lies in the front part of the neck, and 
may easily be felt by applying the hand 
to the neck close under the chin, while 
swallowing. It is covered above b}^ 
the epiglottis; the openings from the 
pharynx into the larynx and the oesopha- 
gus being so arranged that when the 
one is opened the other is closed. 

The larynx consists of the large thy- 
roid and cricoid cartilages together with 
the two arytenoid cartilages which rest 
on the back part of the cricoid. It is 
to the arytenoid cartilages that the 
vocal cords or membranes are at- 
tached. Small muscles fastened to the 
arytenoids regulate their position and 
consequently the tension of the vocal 
cords. As the air is drawn through 
these thin membranes it is vocalized by the latter under 
different degrees of tension. 

The voice thus produced and modified by the nose and 
the various structures in the mouth gives rise to all those 




WHDPIPZ 



Fig. 65. — Larynx 
and windpipe. 



152 PHYSIOLOGY AND HYGIENE 

modulations and inflections that render human speech 
marvelous in the extreme. Inasmuch as the larynx is 
the seat of the ♦production of the voice it is frequently 
called the voice box. 

The Windpipe. — Extending downward from the larynx 
is a tube about four or five inches long and from three 
quarters of an inch to an inch in diameter. This tube con- 
sists of a number of incomplete rings of cartilage with the 
openings toward the back; the rings are bound together by 
tough connective tissue. 

The windpipe and the oesophagus are so arranged that 
the latter can, when distended with food, move forward into 
the openings of the cartilaginous rings. The windpipe and 
the oesophagus are not in use at the same time, and by this 
nice arrangement less space is required for these two tubes 
than otherwise would be. As it is, the neck is slender and 
graceful and permits of a free and easy motion of the head. 

The trachea is lined throughout with a mucous mem- 
brane which secretes a mucus. In addition to the mucous 
cells there are many specialized ciliated cells whose func- 
tion it is to catch dust and other foreign particles and 
drive them from the tube through the mouth. Small cilia 
or hairlike structures extend from these cells into the 
windpipe, and, moving back and forth in unison like waving 
fields of grain, catch up the mucus with its load of dust 
and push the sticky mass slowly upward toward the pharynx 
from which it is forcibly removed by coughing and spitting. 
While the walls of the trachea contain a few plain muscle 
fibers, it can be moved only by moving the head and 
neck. 

Bronchi. — At its lower end the windpipe divides into 
two parts constructed very much like the windpipe it- 



RESPIRATION 



153 



self ; these parts are the bronchi. The rings in the 
bronchi, however, are complete and the walls are rigid over 
their entire surface. Like the windpipe the bronchi serve 
merely as air passages to convey the air to and from the 
lungs. 

Bronchial Tubes and Bronchioles. — After entering the 
lung tissue the bronchi divide and subdivide into the bron- 
chial tubes which have the same structure as the bronchi. 
The bronchial tubes subdivide into numerous minute 
ramifications which extend into every portion of the lung 
tissue. These small subdivisions, called bronchioles, contain 
no rings of cartilage but are made up largely of delicate 
elastic tissue. In the walls of these air passages are im- 
bedded a few plain muscle 
fibers. In the bronchioles 
these fibers are arranged cir- 
cularly so that when they 
contract the diameter of the 
tubes is decreased and the 
supply of air to the lung cells 
is diminished. 

Alveoli or Infundibula. — 
The bronchioles open out 
into small, pear-shaped, sac- 
like structures called alveoli 
or infundibula. The inner 
walls of the alveoli are broken 

up into partly closed pockets or pouches which serve as 
receptacles for the air. The walls of these air cells are ex- 
tremely thin and elastic. 

Surrounding each alveolus and its air cells is a complex 
network of blood capillaries which convey the blood 



ALVEOL 




BRONCHIOLES 



BRONCHIAL 



TUBES 



Fig-. 66. — Bronchial tubes, bron- 
chioles and alveoli. 



154 



PHYSIOLOGY AND HYGIENE 



LARYNX 



WIND -PIPE 



from the pulmonary artery to the pulmonary vein. At this 
point the blood and the air are separated by a single 
layer of cells. It is here that the interchange takes place 
between the blood and the air. That the interchange may 
be carried on in the most perfect manner the inner surface 
of the alveoli throughout the lungs extends over a great 
area and is extremely delicate and elastic. 

The Lungs. — It was suggested on a former page that 
there are really two lungs which are separated by the heart 

and the larger 
blood vessels. 
The lungs are 
concave on 
their lower sur- 
face, fitting 
over the upper 
convex surface 
of the dia- 
phragm. The 
other surfaces 
are convex, 
filling in com- 
pletely the con- 
cave walls of 
the thoracic 
cavity. 

Covering 
every portion 
of each lung 
with the excep- 
tion of the point where the blood tubes enter is a thin 
serous coat called the pleura. A similar coat lines the 




Fig. 67. — Windpipe and lung. 
a, bronchioles; b, alveoli; c, bronchial tube. 



RESPIRATION 155 

inner walls of the thoracic cavity. These layers secrete a 
fluid which lubricates their surface, permitting them to 
glide over each other with but little friction. 

The lung tissue is soft, elastic, and spongy. It is much 
the lightest portion of the body, floating readily on water 
even after being crushed and compressed by the hand. 
At the inner side of each lung a little above the middle, 
the bronchus and blood tubes enter. These form the root 
of the lungs and constitute their only point of attachment. 
The lungs are brownish in color and are continually under 
the strain of the inclosed air. Each lung is pyramidal in 
shape and extends slightly above the collar bone in the 
thorax. 

Process of Respiration. — The act of respiration consists 
of two parts, inspiration and expiration. At the beginning 
of the process the diaphragm contracts, pulling its upper 
convex surface down until it is almost flat. At the same 
time the intercostal muscles contract, lifting the sternum, 
with its attached ribs, upward and forward. The ribs are 
attached and curved in such a way that when the sternum 
is lifted in front they are rotated outward and upward to the 
side. In this way the size of the thoracic cavity is in- 
creased in three different directions; upward and downward, 
forward and backward, and laterally. If the hands be 
placed on the front and side of the chest cavity the forward 
and lateral movements may readily be observed during a 
deep inspiration. 

As the capacity of the thoracic cavity increases, the pres- 
sure of the atmosphere from without drives air through the 
mouth and other passages into the lungs, swelling their 
elastic tissue out until they fill the entire space. This is 
the process of inspiration. 



156 PHYSIOLOGY AND HYGIENE 

When the gaseous interchange has taken place in the 
alveoli, the muscles relax, permitting the diaphragm to 
resume its convex shape, and the sternum and ribs to re- 
turn to their original position. The capacity of the cavity 
being thus decreased, the air flows quietly out of the lungs 
during the process of expiration. It must be remembered 
that the muscles are in action only during inspiration, 
returning to a state of rest during expiration. 

Number of Respirations. — While the rapidity of breath- 
ing varies in different persons and in the same person at 
different times and under different circumstances, yet the 
process is fairly regular under ordinary conditions. The 
average individual breathes about eighteen times per 
minute. Muscular activity usually increases the rate of 
breathing to an extent dependent upon the degree of 
exertion put forth. In high altitudes where the air is quite 
rare the number of respirations increases. Children usually 
breathe more rapidly than old people. 

Capacity of Lungs. — As in the case of the heart, brain, 
and other organs of the body, the size of the lungs varies 
with the individual. Usually large persons have a large 
lung capacity compared with that of smaller persons. 
Frequently, however, the reverse is true. 

Recently in a certain physiology class experiments devel- 
oped the extraordinary fact that the smallest person in the 
class, a young lady, had the greatest lung capacity. The 
size of the lungs depends to a great extent upon the devel- 
opment of the muscles of respiration. Weak lungs may 
often be strengthened by the vigorous and continued exer- 
cise of the muscles. 

Amount of Air Breathed. — If one were to measure by 
means of a spirometer the quantity of air inspired or ex- 



RESPIRATION 



157 




pired during a single breath he would discover that about 
thirty cubic inches flow in or out while the person is engaged 
in ordinary activities. Since this air moves with the regu- 
larity of the ebb and 
flow of the tide, it is 
called tidal air. 

By stimulating the 
muscles of respiration to 
vigorous action a forced 
inspiration will permit 
about one hundred cubic 
inches of air to be in- 
haled in addition to the 
tidal air; this is called 
the complemental air. 

One hundred cubic 
inches of air may be 
forcibly expelled from 

the lungs after an ordinary expiration; this is known as 
the supplemental air. 

After all efforts have been exerted to expel the air from 
the lungs, there still remains about one hundred cubic 
inches called the residual air. 

Since a person has control over the tidal, the comple- 
mental, and the supplemental air, the combined capacity 
of the three is called the vital capacity. The total amount 
that may be breathed in and out, then, at a single breath 
is 230 cubic inches, while there is left in the lungs always 
at least one hundred cubic inches of residual air. 

Result of Respiration. — It has already been suggested 
that the chief object of respiration is to supply the blood 
with oxygen. This is accomplished by the transference of 



Fig. 68. — Diagram showing- amount Of 
different kinds of air in lungs. 



158 



PHYSIOLOGY AND HYGIENE 



the oxygen through the delicate walls of the alveoli 
when the fresh air is taken in. It may be said here that, 
although the air is about four-fifths nitrogen, not any 



CAPILLARY 




Fig-. 69. —Diagram of alveolus. 

of this gas gets into the body through the lungs. What- 
ever nitrogen gets into the tissues passes in as a part of the 
food. 

It is necessary that the waste matter, resulting from the 
torn-down cells, be eliminated from the system. A portion 
of the impurities is cast out through the skin and the kid- 
neys; a part is eliminated through the lungs. A careful 
analysis of air before and after it is breathed shows that 
while it is made up largely of nitrogen and oxygen before 



RESPIRATION 159 

being taken in, it contains variable quantities of impurities 
after being thrown out. 

Water Vapor. 1 — That expired air contains a considerable 
quantity of water is proved on cold, frosty mornings when 
the moisture of the breath is changed to frost which appears 
as a white cloud. When the breath strikes cold objects, 
such as a mirror, the moisture is condensed to a liquid. The 
water vapor in the breath can hardly be called an impurity. 
Its presence is rather incidental to respiration. 

Carbon Dioxide. — This gas, sometimes called carbonic- 
acid gas, is always present in expired air. It is usually con- 
sidered poisonous, but its injurious effects in the air are due 
more to the fact that its presence excludes the necessary 
oxygen than to the fact that it is a poison. That the breath 
contains carbon dioxide may be shown by breathing through 
clear lime water by means of a straw or glass tube. A 
white substance very much like pulverized chalk appears 
and settles to the bottom of the liquid. 

Organic Matter. — The really poisonous nature of ex- 
pired air depends upon the presence of minute particles of 
organic matter that have been thrown from the body into 
the lungs. While these particles are too small to be seen 
readily, their presence is easily determined by breathing 
into a closed vessel which is then kept in a warm place for 
a time. The organic matter soon decomposes into gases 
which give rise to a disagreeable odor when the vessel is 
opened. The gases formed in this way are quite poisonous. 
For this reason rooms with occupants should be carefully 
ventilated. 

1 In 100 parts of water escaping from the body about 48 parts are 
lost through the kidneys, 30 through the skin, 18 through the 
lungs, and the remaining parts from the alimentary canal. 



160 PHYSIOLOGY AND HYGIENE 

Heat. — The impurities mentioned above are different 
forms of matter. It is interesting to note that energy in the 
form of heat is lost from the body through expired air. 
That this is true is proved by throwing the breath into the 
palm of the hand ; the breath is quite warm even though the 
air breathed in was very cold. A large assembly room, the 
air of which seems chilly when unoccupied on a cold day, 
becomes comfortably warm when filled with people. The 
heat which warms the air comes from the lungs and skin. 



CHAPTER XX 

DISEASES OF THE LUNGS— VENTILATION 

Diseases of the Lungs. — Almost all parts of the body are 
subject to disease and decay, but the lungs, on account of 
their delicate structure, are the prey of more diseases than 
almost any other organ. 

Asthma. — The nature of asthma is not fully understood, 
but many believe it to be caused by the abnormal contraction 
of the plain muscle fibers surrounding the small bronchial 
tubes or the bronchioles. As the result of this contraction 
the diameter of the tubes is reduced and the free access of 
air prevented. Since the supply of oxygen is thus decreased 
the individual attempts to breathe harder and the in-rush 
of air through the small tubes produces the whistling or 
wheezing sound so characteristic of asthmatic persons. 

Many remedies have been suggested for asthma, but in 
most cases an entire change of climate is necessary. Even 
then the person afflicted " wears out" the climate and 
another change must be made. 

Bronchitis. — Often a "cold in the head" never gets 
beyond the throat. Frequently, however, the cold works 
its way down the trachea and into the bronchi irritating 
and inflaming the mucous membrane of these parts. A 
cold in this stage is called bronchitis. Of course, the cold 
and the bronchitis are both the result of exposure in some 
way. The throat and breast should be carefully protected 
and in severe cases, a physician should be consulted. 

161 



162 



PHYSIOLOGY AND HYGIENE 




Fig-. 70. — Bacteria 
of consumption. 



Consumption. — One of the most dreaded and fatal dis- 
eases to which the body is prey is consumption or tuber- 
culosis of the lungs, formerly better known b}^ the term 
phthisis. This is a gradual wasting 
away of the tissues of the lungs, usually 
beginning at the apex. 

An old view held that small tubercles 
formed in the lung tissue; these finally 
decomposed. In this way the lungs 
were gradually destroyed. 

The modern theory is that consump- 
tion is a germ disease and that the de- 
struction of the lungs is due to the eating away of the 
alveoli and bronchioles by a specific kind of bacteria. 
The many cases of consumption and its extreme deadliness 
have attracted the attention of physicians and scientists 
all over the world. People everywhere, both the sick and 
the well, are watching with anxious interest the result of 
the present investigation of the causes and cure of the 
" white plague." 

While authorities differ in regard to the real nature of 
consumption, all agree that its ravages may be checked and 
its attacks prevented in many cases. Wherever symptoms 
of the disease make their appearance, the greatest care 
should be taken to see that the surroundings, both indoors 
and out, are such that they will prevent its further devel- 
opment. Good ventilation, clean rooms, healthful food, 
sanitary cellars, fresh air, and plenty of exercise are all 
enemies to the development of consumption. Even after 
tuberculosis has reached an advanced stage its ravages may 
be checked by intelligent treatment. 

Where the disease has not advanced too far and the 



DISEASES OF THE LUNGS— VENTILATION 163 

atmospheric conditions are not too different, a change of 
climate is often advisable. The great fight against con- 
sumption, however, is a fight for prevention. Clean sur- 
roundings and fresh air and sunshine are the strongest 
weapons at our command. 

Diphtheria. — This is a term applied to an acute in- 
fectious disease of the throat in which a leathery membrane 
forms on the mucous membrane. This is not properly a 
disease of the lungs, but is discussed here as a matter of 
convenience. There are some who regard diphtheria pri- 
marily as blood poison. A more popular idea, however, 
is that the basis of the disease is in the throat and that the 
blood poison is merely incidental. Physicians now quite 
generally agree that it is a bacterial disease; in fact, the 
germs have already been discovered and carefully studied. 

Diphtheria is usually a disease of childhood, but older 
persons are often subject to it. If a child should complain 
of its throat and any of the symptoms of diphtheria are pres- 
ent a physician should be called at once. 
In the meantime, sulphur should be 
blown against the affected spot or the 
throat sprayed with hydrogen peroxide 
if the material is at hand. If the dis- 
ease has progressed toward the critical 
stage an antitoxin is now usually admin- 
istered to neutralize the effect of the Figr ; l x ; " * ac . teria 

of diphtheria. 

condition. From the very beginning 
the throat should be carefully protected from exposure. 
Pleurisy. — As the term suggests, this is a disease of the 
pleura. Often the delicate membranes of the lungs become 
inflamed and as the two pleurae rub over each other, intense 
pain results. While pleurisy rarely if ever proves fatal it is 




164 PHYSIOLOGY AND HYGIENE 

an exceedingly painful disease. It seems that little is 
known of the cause of the inflammation and little can be 
done for its relief. A knowledge of atmospheric conditions 
is sometimes of value; moisture in the air aggravates 
the condition. A cold is also liable to increase the in- 
flammation. 

Pneumonia. — Aside from consumption, pneumonia 
claims more victims annually than any other disease of the 
lungs. While consumption may drag its course along 
through a series of years, pneumonia is quick and fatal. 
Pneumonia is the inflammation of the tissue of the lungs, 
but particularly of the delicate walls of the alveoli. Death 
results not so much on account of the disease itself as the 
fact that the inflammation of the walls does not permit 
of the proper exchange of the gases between the air and 
the blood and thus the supply of oxygen to the blood is 
shut off. 

The disease usually begins with a cough and pains in the 
region of the lungs. These are accompanied by slight con- 
vulsions, rapid rise of temperature, and quickened pulse. 
The specific treatment depends upon the particular mani- 
festation of the disease. Action, however, should be prompt, 
as the developments are rapid and death results in a short 
time. A competent physician should be called in im- 
mediately and every means taken to check its advance 
in its earlier stages. It is hardly necessary to say that 
pneumonia is usually preceded by a cold or severe case of 
bronchitis. 

Ventilation. — If we were to live day and night in the 
open air or in loosely constructed huts as savages do, 
there would be no need to give attention to ventilation. 
In our modern buildings, however, where the windows and 



DISEASES OF THE LUNGS— VENTILATION 165 

doors are made almost air tight, the subject is of extreme 
importance. How often have we gone into a closed room 
that fairly reeked with offensive and disagreeable odors! 
How many times have we observed persons, overcome by 
the foul atmosphere of a crowded building, grow faint 
and leave the house in order to get fresh air! Too often, 
the drowsiness of a church congregation is due to a lack 
of a sufficient supply of fresh air and invigorating oxygen. 

During cold weather people often close doors and windows 
in order to keep the room warm, forgetful of the fact that 
while they keep the heat in, they shut the oxygen out. 
Instances have been cited of jails, crowded with prisoners, 
which were tightly closed up with the exception of one or 
two very small windows, with the result that many of the 
men died during a single night. A short time ago while 
a storm was in progress the rooms of a large steam vessel 
were shut up; when the storm had passed and the rooms 
were opened it was found that a number of people had died 
and many more had fainted away for want of fresh air. 

Even though the results may not prove serious at once, 
it is well to remember that breathing in impure air will 
finally undermine the whole system and impair the health 
permanently. To prevent such results we should know 
something of correct methods of ventilation. 

How to Ventilate Our Homes. — Many of our modern 
houses are ventilated in connection with furnaces. Most of 
our houses, however, must be ventilated in some other way. 
The old-fashioned fireplace with its broad chimney and 
blazing fire was an excellent means of carrying off the 
impure air. Cook stoves and heaters also tend to purify 
the atmosphere of the room. As the warm air passes out 
through the flue, the cold air comes in through cracks in 



166 



PHYSIOLOGY AND HYGIENE 



BOARD 



windows and doors. But we should not leave the matter 
of ventilation to the stoves and fireplaces. Special attention 

should be given to che adjust- 
ment of windows to the end 
that plenty of air may get in. 

It is needless to say that 
the openings should not be as 
large on windy days as on quiet 
sultry ones. On cold windy 
days sufficient ventilation may 
be obtained through the cracks 
around the sashes and doors. 
Usually it is better to have the 
windows opened slightly. A 
good plan is to raise either the 
upper or the lower sash and in- 
sert a board that just fits the 
opening. This leaves a narrow 
slit between the two sashes for 
the entrance of the air. An- 
other method is to raise the lower sash of one window 
slightly and lower the upper sash of another window about 
the same distance. The cold, pure air will come in through 
the first while the warm, polluted air will pass out through 
the second. Bedrooms require especial care since we spend 
about one third of our time there. The beds should be sup- 
plied with plenty of covers and then the windows should 
be opened far enough so that an abundance of fresh air 
can get in. In all cases, however, draughts should be 
avoided. 

Ventilation of Public Buildings. — But few of our churches, 
schooihouses, and other public buildings are properly 



Tig. 72. — Arrangement of 
window for ventilation. 



DISEASES OF THE LUNGS—VENTILATION 167 

ventilated. It is not difficult to get at the cause of the 
languor and drowsiness that come over many public gather- 
ings. It is true that an effort is made in some places to 
provide fresh air, but the effort is usually characterized by 
the grossest ignorance of the laws of ventilation. A window 
is thrown open in such a way as to permit the cold air to 
fall over the heads of the people, chilling them completely 
or giving them severe colds. Frequently such a draught is 
produced that some one rises from the audience and closes 
the window tightly once more. The ventilation of every 
building should be placed in the hands of some competent 
person and he should be held responsible for the results. 

What was said concerning the ventilation of private homes 
will in a measure apply here. If the air on the outside is 
quiet, windows may be raised or lowered in almost any part 
of the building. When the wind is blowing the windows 
should be opened on the opposite side from the wind. If 
each of several windows be raised or lowered just a little, 
the exchange of air will take place without producing a 
draught over anyone. The ideal method, of course, would 
be to have a system by means of which fresh air is taken in 
and warmed before being thrown into the room. The forc- 
ing of the air into the room will drive the impure air 
out. 

Whatever may be said of the method of ventilation, the 
important thing to be remembered is that there must be a 
frequent and complete exchange of the air. When the 
heating apparatus is not arranged to provide for this ex- 
change, some method must be improvised to meet the de- 
mands of the occasion. 

Alcohol and Respiration. — Alcohol dries up and hard- 
ens the delicate walls of the alveoli, preventing the inter- 



168 PHYSIOLOGY AND HYGIENE 

change of gases between the air and blood. As the blood 
gives off carbon dioxide and other gases and takes on 
oxygen, the effects of alcohol on respiration are seen to be 
far reaching. 

Tobacco and Respiration. — One of the most serious 
effects of narcotics in the body is observed in connection 
with smoking. Tobacco smoke is drawn into the lungs and 
as it passes through the windpipe and bronchial tubes it 
inflames and tans the membrane lining these tubes, often 
producing " smoker's" cancer. In addition it fills up the 
little alveoli with deposits containing nicotine, leaving 
them dried and shriveled. The effect is to prevent the 
interchange of gases in the lungs. 



CHAPTER XXI 

EXCRETION 

Waste Matter. — After a carpenter has worked some time 
in his shop a large amount of shavings, blocks, and sticks 
accumulates. The farmer who runs a thrashing machine 
finds it necessary to repair the machine from time to time 
and the old fragments of wood and iron are thrown into 
a pile in the back yard. As the coal burns in the kitchen 
stove, the ashes gather in the pit below. Wherever labor 
and work are carried on we observe an accumulation of 
waste matter. The human body is a great machine in 
which the various organs are constantly at work. As the 
different organs perform their functions the cells of which 
.they are made are broken down, the tissues decomposed, 
and a large amount of waste matter is the result. 

Organs of Excretion. — The process by which the waste 
matter from broken-down cells is thrown out of the body is 
called excretion. The organs that take part in the elimi- 
nation of this waste matter from the body are the lungs, the 
liver, the kidneys, and the skin. The relation between the 
lungs and the liver and excretion has already been dis- 
cussed. A study of the kidneys and the skin will now be 
made. 

The Kidneys. — The kidneys, two in number, are reddish- 
brown organs lying against the back walls of the abdominal 
cavity. They are bean-shaped structures about two inches 
wide and four inches long and lie with the hollow edges 

facing each other. 

169 



170 



PHYSIOLOGY AND HYGIENE 



Structure. — The structure of the kidneys is made up 
largely of three layers. The outer one is called the capsule 
and is a thin transparent layer of connective tissue which 
closely covers the whole kidney with the exception of the 
point where the tubes emerge from the organ. 

The second layer is a reddish, granular area which shines 
through the transparent capsule and gives the color to the 



OESOPHAGUS 




INFERIOR 
VENA CAVA 



RIGHT KIDNEY 



DESCENDING C0L0M 



Fig. 73. — Kidneys in position. 



kidney. The granular appearance is due to the presence 
of capillaries from the renal artery which surround the 
enlarged beginnings of the uriniferous tubules. These little 
nodules, called Malpighian corpuscles, are packed closely 
together and are the organs through which the material 
to be eliminated from the blood is secreted. This layer, 
on account of its similarity to the bark of a tree, is called 
the cortical layer or the cortex. 
The inner coat, called the medulla, is made up of fine 



EXCRETION 



171 



glistening threads which under the microscope resolve 
themselves into the uriniferous tubules mentioned above. 
These tubules cross the medulla and empty into a cavity 
called the pelvis, which lies close to the concave or inner 
side of the kidney. 
Several prominences, 
known as pyramids, 
project into this cavi- 
ty. The hollow por- 
tion, corresponding 
to the scar on the 
bean through which 
the tube passes that 
carries away the 
waste matter, is 
called the hilum. 

Function of the 
Kidneys. 1 — The kid- 
neys serve to elimi- 
nate certain waste 
matter which cannot 
be eliminated by the 
other organs of ex- 
cretion. The small capillaries from the renal artery 
closely surround the uriniferous tubules. The solid 
particles, which are to be cast out, get from the blood 
of these capillaries into the tubules. At the same time 

1 Many of our texts state that the blood is pure after it has reached 
the left auricle from the lungs. The blood at this point still con- 
tains some impurities. It is evident that no impurities are re- 
ceived by the blood as it passes from the heart down through the 
aorta. The kidneys get their supply of blood directly from the 
aorta through the renal arteries; as the kidneys are organs of ex- 




Fig. 74. — Section of kidney. 



172 PHYSIOLOGY AND HYGIENE 

water is thrown from the blood into the Malpighian cor- 
puscles, and flowing through the small tubules, washes the 
solid portions into the pelvis and out of the body. 

Waste Products. — By far the largest portion of the 
material excreted by the kidneys is water. The chief solid 
portion already mentioned is a white salt called urea. In 
addition there are: uric acid, mineral salts, and certain 
aromatic compounds. 

Importance of Healthy Kidneys. — Of the organs of ex- 
cretion the kidney is probably the most important, hence 
anything that tends to affect its perfect action interferes 
materially with the elimination of those waste products, 
the accumulation of which in the system would result in 
diseases of different kinds. When muscle tissue is disinte- 
grated by exercise or when the excess of proteid is broken 
down in the liver a considerable portion of nitrogenous mat- 
ter is thrown into the blood. If this excess of nitrogenous 
matter is not removed from the body it becomes the seat of 
disorders that are serious in the extreme. Since the larger 
portion of urea is cast off through the kidneys it is very 
important that these organs be kept in a healthy condition. 

Bright's Disease. — In the preceding paragraph was men- 
tioned the fact that an accumulation of nitrogenous matter 
in the body leads to a serious disorder of the system. The 
condition resulting from the presence of a large quantity 
of albumen in the secretions from the kidneys has been 
called Bright's disease in honor of the man who first made 

cretion it seems clear that they could not eliminate waste matter 
from the blood if it were pure when it reached them. Since the 
blood has impurities taken from it in the kidneys and passes at once 
to the ascending vena cava through the renal veins, it would appear 
that the purest blood in the body is in these veins and not in the 
pulmonary veins. 



EXCRETION 173 

a study of the subject. While much has been learned by 
the scientists concerning the cause of Bright's disease, but 
little of real value has been determined regarding its cure. 
One who has this disease should discard all foods that con- 
tain large quantities of proteids or albumens. The amount 
of urea then liberated would be much lessened. 

The Skin. — Another organ of excretion is the skin, or 
integument. This fairly thick, tough structure covers the 
whole body and, with its modifications, the hair and the 
nails, performs other functions than that of excretion. It 
is composed of two principal layers, the cutis or dermis and 
the cuticle or epidermis. 

The Cutis. — When the skin of an animal is tanned and 
made into leather the part that gives it strength and tough- 
liess is the cutis. Since it is the real substance of the in- 
tegument it is called the true skin. The dermis is made up 
of a mass of tough white fibers and yellow elastic con- 
nective tissue bound firmly together. The fibrous charac- 
ter may easily be determined by shredding a loosened piece 
of leather. The fibers are also elastic as may be proved by 
grasping the skin on the back of the hand and stretching it. 
Scattered among the fibers are veins, arteries, lymphatics, 
nerves, sebaceous glands, and perspiratory glands. 

The dermis is held to the underlying structure by the 
tough areolar tissue. Frequently this is filled with fat 
cells, forming what is known as adipose tissue. 1 The 
surface of the dermis is not smooth as it might seem to be, 

1 Wrinkles are produced as a result of the disappearance of the 
adipose tissue from beneath the skin. In young persons the skin 

I is kept smooth by the excess of fat beneath the dermis. As old age 
approaches this fat is carried away and the flabby skin is thrown 



174 



PHYSIOLOGY AND HYGIENE 



but is covered with many small projections called papillae. 
Each papilla contains blood vessels, nerves, and touch 
corpuscles. These papillae are very sensitive. Their sensi- 
tiveness and peculiar location admirably fit them for organs 
of touch. The characteristic regular lines in the palm of 
the hand are merely rows of these papillae pushing the 
epidermis up from beneath. 

The Cuticle. — The cuticle or epidermis rests upon the 
dermis. Since it is regularly worn away and does not seem 



OUCT 




EPIDERMIS 



RA"LPIGHIAH* 



DERMIS 



SWEAT GLAND 



•BLOOD TUBE 
Fig-. 75. — Cross section of skin. 



to enter into the substance of the skin proper, it is often 
called the false skin. The cuticle is really made up of two 
layers, the clear, outer, horny layer, called the stratum 
corneum, and the inner layer of rounded cells, known as 
the Malpighian layer. 



EXCRETION 175 

Contrary to the prevalent idea the epidermis is not an 
outgrowth of the dermis, but is developed from the lower 
row of cells in the Malpighian layer. These globular cells 
as they increase in number move outward, becoming flat 
and transparent as they approach the surface of the epi- 
dermis. 

There are no nerves nor blood vessels in the scarf skin, 
hence it is not sensitive to pain. Nerve endings from the 
dermis, however, stick up between the lower cells of the 
epidermis; when the latter is rubbed off, as in a bruise or 
blister, these delicate nerves are affected by bodies or air 
coming in contact with them and pain is the result. The 
color pigments which determine the complexion lie in the 
lower cells of the epidermis. Constant rubbing or friction 
produces a thickening of the cuticle as may be observed in 
the palm of the laborer's hand and the sole of the barefoot 
boy. 1 

Sebaceous Glands. — The surface of the skin and the hair 
is often covered with an oily substance that makes these 
structures soft and pliable. This oil is secreted by the seba- 
ceous glands. These are rounded, grapelike clusters of cells 
imbedded in the dermis and filled with little particles of 
fatty material. The ducts lead into the hair follicles or out 
on the surface of the skin. In some persons an excessive 

1 A corn is a thickening and hardening of the epidermis. Corns 
are frequently hornlike and transparent, usually containing a cen- 
tral core or nucleus. They are produced by pressure or friction. 
If the pressure is removed, the corn will loosen and may be pulled 
off. Corng usually form on the feet and are very painful. Warts 
are affections of both the dermis and epidermis. The enlarged 
papillae of the dermis push up through the epidermis and often 
present an uneven surface that at times is annoying and even 
painful. 



176 



PHYSIOLOGY AND HYGIENE 



amount of oil is secreted while in others not enough is 
thrown out to keep the skin and hair from breaking or 
cracking. The Meibomian glands lying between the hairs 
of the eyelashes are the largest oil glands in the body. 

Perspiratory or Sweat Glands. — Scattered over the sur- 
face of the body are thousands of small slender .tubes that 
lead from the lower portion of the der- 
mis to the exterior. At the lower end the 
tube is thrown into many interlacing coils 
which are in close contact with the blood 
capillaries. It is here that the secretion 
from the blood takes place. The coiled 
tube rises spirally through the dermis 
and the epidermis opening, as already 
stated, on the surface. The tube is coiled 
up in a bunch in order to give as great 
a secreting surface as possible. 

Perspiration. — The secretion from the 
sweat glands is like that from many other 
glands in the body in that it is composed 
largely of water. The other constituents 
are common salt, urea, carbon dioxide, 
and a few substances that are present in 
small quantities. The function of the 
water is to wash out the solid portions from the gland so that 
it may be kept clean and in a healthy condition. 

The amount of sweat eliminated by these glands is de- 
termined by conditions. During vigorous exercise when 
the body becomes warm a large amount of perspiration 
is thrown upon the surface, a portion of which evaporates 
and takes up heat, thus cooling the body. At other times 
the amount secreted may be so small as to be unobserved ; 







EXCRETION 177 

this is called insensible perspiration. It is known as 
sensible perspiration when it collects as a film or in drops 
on the skin. 

The Complexion. — Whether or not a person is of light 
or dark complexion depends upon the nature and character 
of the color pigments in the skin. It has already been said 
that these color pigments lie in the Malpighian layer of the 
epidermis. The coloring matter in a dress and the paint on 
a house are affected when subjected to a continued action 
of the sun's rays, in many cases fading materially. The skin 
undergoes a change of color as a result of long exposure to 
the light of the sun, turning brown or,. as we say, "" tanning." 

Invalids and others who are compelled to remain for 
some time in darkened rooms take on a very light com- 
plexion, just as a plant that grows in a dark cellar assumes 
a white or faded appearance. 

Usually there is a close relation between the color of the 
pigments in the hair, eyes, and skin. Brunettes, or those 
who have dark skins, usually have black hair and dark or 
black eyes. Blondes generally have light skins, light hair, 
and blue eyes. However, there are marked exceptions to 
these relations. 

Persons who have a light complexion ordinarily have skins 
that easily redden or blister when exposed to the heat of the 
sun. In some people the color pigments are of such a 
nature that the coloring matter seems to collect into small, 
irregular blotches, producing freckles or discolorations. 

A peculiar freak of nature is the albino, in whose eyes and 
skin the color pigments seem to be wanting entirely. An 
albino has a milky or white skin, light hair, and pink eyes. 
Albinos occur among all races and in many of the lower 
animals; white mice and white rabbits are albinos. 



178 



PHYSIOLOGY AND HYGIENE 



stratum of malpighi v, 
external root-sheathj; 
second external- 
root-sheath 
internal 
root-shea! 

fibroid sheath 
medulEa 



Modifications of the Skin. — There are two specialized 
forms of the skin, namely, the hair and the nails. A careful 
study reveals the fact that these structures are outgrowths 

of the epidermis and have devel- 
oped in these peculiar ways to per- 
form certain functions in connec- 
tion with the body. 

The Hair. 1 — Covering the whole 
body, with the exception of the 
palms of the hands, the soles of the 
feet, and the tips of the fingers and 
toes, are many long slender fila- 
ments called hairs. A single hair 
is much like some kinds of plants, 
a pith within, a fibrous portion 
next, and a layer of flattened cells 
on the outside. The hair is some- 
what elastic and is quite tough and 
strong in comparison with its diam- 
eter. The hairs are set in pits or 
depressions of the skin much as 
fence posts are set in the ground. 
These depressions are called hair 
follicles and are formed by cells of 
the epidermis dipping down into the dermis, so that, while 
the hair roots are imbedded in the true skin, they are really 
developed from the epidermis. 

1 The hair grows sometimes to an enormous length. Beards have 
been known to reach almost to the ground, while the hair of some 
ladies touches the floor when loosened. In southern France peas- 
ant girls cultivate heads of hair which they sell at fancy prices, to 
be used in head decorations. Instances are on record of hair being 
cut that had grown over six feet in length. 




FIBRO-VASCULAR 
SHEATH 



BLOOO-VESSELS^g 
OF THE HAIR-PAPILL/ 



Tig-. 77. — Magnified hair 
and root. 



EXCRETION 



179 



Hairs are enlarged at the base and are supplied at that 
point with blood vessels for their nourishment. Instead 
of being set perpendicular, the hairs are inclined somewhat. 
They may be brought more nearly to an erect position 
through fear or cold by the action of small muscles which 
are fastened to their sides and imbedded in the substance 
of the dermis. The hair grows from within outward, and 
may be cut or broken without pain. Evidently the hair 
is in intimate relation with nerves at its base. 

The shape of the hair varies from round in the Asiatic 
to oval in the European, the curliness of the hair of the 
latter being due to the oval shape. The 
number of hairs on the human head 
varies from 100,000 to 125,000. 

The Nails. — Capping the ends of the 
fingers and toes on the upper side are 
rounded horny structures called nails. 
These, as has already been stated, are 
developed from the epidermis of the 
skin. At the base of the nails the epi- 
dermis folds in and back, forming a kind 
of pocket from which the nails develop: 
A thin sheet of this hard, hornlike sub- 
stance grows from this pocket toward 
the extremity of the finger, increasing in 
thickness at the ends. While the nails 
are insensible to pain the tissue under- 
neath, or the " quick," is extremely 
sensitive to the touch. The light pink color of the nails is 
due to the blood underneath showing through the trans- 
parent structure. If the cells in the pocket are not de- 
stroyed the nail will be reproduced. It takes from three 




Fig. 78.— Cross sec- 
tion of finger 
showing nail. 

A, nail; B, pocket from 
which nail grows ; C, 
cuticle ; D, cutis ; E, 
fatty tissue; F, bone. 



180 PHYSIOLOGY AND HYGIENE 

to five months for a nail to develop fully after it is re- 
moved. The nails add beauty and symmetry to the fingers 
and hand, and, on account of their arrangement, are ad- 
mirably suited to picking up small objects. 

Functions of the Skin. — As was stated in another para- 
graph, the skin has several uses. It is primarily an organ 
of protection. Were it not for its presence the delicate 
organs and tissues lying under it would constantly be sub- 
jected to the action of atmospheric agencies and to the 
dangers arising from physical causes. As it is, the thick, 
tough integument covers the whole body, shielding the 
sensitive parts from all harm. In addition to its use as an 
organ of excretion, the skin serves to regulate the tempera- 
ture of the body as discussed under the subject of perspi- 
ration. 

While the skin is an excretory structure it also has the 
power to absorb substances through its pores. We are all 
familiar with the fact that the value of a liniment depends 
upon the power of the skin to absorb some of its ingredi- 
ents. Paint is sometimes taken through the pores, giving 
rise to a case of poisoning. It is a well-known fact that 
water may be taken into the system and thirst partially 
quenched by submerging the body in water that is unfit to 
drink. 

Moreover, the skin contains the end organs of touch, 
and hence is essentially the organ in which arise those 
sensations that give us, in connection with the other senses,, 
our ideas of size, hardness, smoothness, roughness, etc. 

Finally, the skin is a structure that gives beauty and 
symmetry to the body. It covers up the unsightly bones, 
tendons, muscles, and tissues that, uncovered, would be 
unattractive and even repulsive to the eye. 



CHAPTER XXII 

BATHING— DISEASES 

Hygiene of the Skin. — There is no part of the body that 
requires greater care than the skin. It covers the whole 
body, contains the pores through which impurities are 
thrown off, and is the structure which determines to a large 
extent whether or not the body is comely and attractive 
or unsightly and repulsive. 

One thing that distinguishes the cultured and refined in- 
dividual from the uncultured and uncivilized person is the 
care he takes in keeping the skin in good condition. Many 
a man who should know better fails to make friends be- 
cause he permits his person to become so dirty and filthy 
that his appearance is not only unattractive, but even re- 
pulsive. The removal of secretions and deposits from the 
skin is indeed a sanitary measure, but it should be considered 
a means of making the person presentable as well. Many 
boys and girls thoughtlessly offend the fine senses of those 
about them by neglecting to keep the body clean. Children 
should be taught from the first that bathing is a duty if 
not always a pleasure. 

Bathing. — The necessity of the bath has been recognized 
from the very beginning of civilization. In fact, the bath 
tub may be considered one of the greatest inventions of 
any time. It has been well said that the civilization of a 
nation might be measured by the amount of soap it uses 
in keeping clean. Some of the greatest nations of antiquity 

181 



182 PHYSIOLOGY AND HYGIENE 

had their finely furnished bathrooms, and a house built in 
these modern days is not considered complete without a 
bathroom or some provision for taking a bath conveniently. 

Value of the Bath. — VCe have already learned that one 
of the functions of the skin is to eliminate certain impurities 
from the system through its pores. When the excretions 
oome to the surface of the skin they frequently harden 
and close up the pores. Unless this hardened material 
is removed further elimination is impossible. As a' result, 
poisonous matter accumulates in the system and the seeds 
of disease are thus sown. 

Moreover, as the cells of the lower part of the epidermis 
grow outward, the outer cells die and should be removed 
or else they, too, will interfere with the perfect action of 
the oil and sweat glands. The dead cells of the epidermis 
may sometimes be seen upon rubbing parts of the body, 
as the arm; the loose cells roll up into small balls under 
the friction of the hand or towel. The vigorous appli- 
cation of water and soap removes the dead tissue of the 
epidermis, and cleans out the pores. This cleansing proc- 
ess puts the skin in a healthy condition, and the pink flush 
produced in the skin by the outflow of the blood makes 
it comely and attractive. 

Kinds of Bath. — A particular kind of bath does not 
always have the same effect on different persons. The 
physical development and nervous condition of the in- 
dividual determine largely the enjoyment he gets from 
the bath. The previous kind and amount of exercise have 
considerable to do with the value of any kind of bath. 
Everyone should stud}' the conditions that surround him 
and adapt the bath to his particular needs. 

Hot Baths. — That the hot bath is preferred by most 



BATHING— DISEASES 183 

people is certainly true. It is valuable in that the hot water 
has a greater dissolving effect upon the impurities lodged 
in the pores of the skin, hence it is easier to cleanse the 
body in this way. Moreover, in cold weather the hot bath 
is more comfortable than is the cold. When the hot water 
is brought in contact with the skin the pores are opened up, , 
the capillaries distended, and a stream of warm blood sets 
in to the surface that gives a healthy glow to the whole 
body. But there is an immediate reaction. The water 
evaporates rapidly from the skin, cooling the surface, and 
causing the blood to flow back to the central organs, leav- 
ing the whole system weakened and depressed. For this 
reason the hot bath should be taken carefully so as to guard 
against serious results. 

It may be observed that the body responds more readily 
to changes of temperature in the water bath than it does 
to changes in the temperature of the air. It has been sug- 
gested that a person can go from an atmosphere below 
freezing point to the hot air of an August day or an oven 
without any serious consequences, but changes of a few 
degrees in the temperature of the water has a marked 
effect upon the system. Unless the body is strong and 
robust it should not be subjected to quick and great 
changes of temperature in the bath. 

Effect of Different Temperatures. — If the temperature of 
the water be raised to that a little below the normal tempera- 
ture of the body the bath may be prolonged an indefinite 
time without serious consequences. Within the tempera- 
ture limits of 85° and 95° only the nerve endings lying 
in the skin are affected, the central organs being undis- 
turbed. For this reason there is no marked change in 
the temperature of the body, consequently no reaction 



184 PHYSIOLOGY AND HYGIENE 

can set in. The tepid bath is adapted to invalids and 
nervous individuals. 

When the water is raised to 95° or 100° the effect is im- 
mediately felt by the central organs and a reaction takes 
place in which the blood flows to the surface, producing a 
feeling of warmth. As the temperature of the water is 
raised the reaction increases in intensity, the pulse quickens, 
the blood surges to the capillaries of the skin, and the per- 
spiration flows in abundance. If the system is not too much 
depressed by the reaction, the result of a hot bath is bene- 
ficial, inasmuch as the pores of the skin are thoroughly 
opened and the process of excretion is very much im- 
proved. Long-continued hot baths, however, are liable to 
produce drowsiness, fainting, congestion, and exceptional 
cases of apoplexy. 

Cold Baths. — Any bath below 80° may be considered 
a cold one. The immediate effect of a cold bath is to 
drive the blood from the surface to the interior of the 
body. The pulse slows up, the capillaries contract, and 
the skin becomes pale or blue. If the shock of the 
cold water is not too severe the reaction soon sets in, 
the blood rushes to the capillaries of the surface, the 
skin reddens, and the body feels strengthened and re- 
freshed. 

Whatever may be said of the value of the cold bath it 
should be short. If the water be too cold and the bath 
long-continued, the results may prove fatal to those who 
are unable to withstand the first shock. Cold baths are 
always dangerous to those who are exhausted or weakened 
from fatigue. Where the internal vital organs are weak 
or diseased the cold bath is liable to produce a congestion 
of those organs that may result fatally. 



BATHING— DISEASES 185 

Time for a Bath. — Persons of sound bodies and strong 
nerves will find the evening, just before retiring, a very 
convenient and suitable time for the bath. Many find it 
more desirable to take it just after rising in the morning, 
believing that if it be taken regularly at this time, all danger 
of taking cold will be eliminated. In any event, the bath 
should never be taken immediately after a meal when the 
stomach is full and the digestive fluids flowing. Every 
person should determine for himself by experience the time 
which is most suitable for bathing. 

Diseases of the Skin. — Owing to the great exposure to 
w T hich the skin is subjected it is the seat of many diseases. 
While some of these disorders are unimportant, many of 
them are of extreme interest on account of the fact that 
they may effect materially the general health of the body, 
and further, that they tend to make the skin unsightly. 
Moreover, many skin diseases are intimately connected with 
deep-seated disorders within the body that are serious in 
the extreme. A few of the more important diseases of 
the skin will be mentioned briefly. 

Erysipelas. — A disease of the skin in which there is 
extended inflammation with fever is erysipelas. Frequently 
the disorder breaks out around a wound, but often it 
appears without any connection with a cut or abrasion. 
The skin at first appears red, becoming hard and thick. 
Gradually the condition spreads to the surrounding integu- 
ment, the part becomes heated and inflamed, and pain of 
greater or lesser intensity sets in. Finally, the affected 
portion grows lighter in color and the dead cells begin to 
loosen and drop off. 'Erysipelas is an extended and 
serious disease, disfiguring the features, in many cases, 
of the person who is suffering from it. Besides, it is liable 



186 PHYSIOLOGY AND HYGIENE 

to cause a derangement of the vital organs, producing 
death. 

Eczema. — This is a less serious affection of the skin than 
erysipelas, in which there is a breaking out and inflamma- 
tion followed by the formation of vesicles and secretions of 
lymph. It manifests itself in various ways, but is not often 
necessarily serious. It is usually accompanied by itching 
and more or less irritation. 

Measles. — Measles is a -contagious disease which is not 
primarily an affection of the skin, but is mentioned here 
because it manifests itself on that structure. Usually from 
nine to ten days elapse from the time of exposure to the 
breaking out of the disease. The period of development ex- 
tends over three or four days and is accompanied by an inflam- 
mation of the mucous membrane of the eyes, nose, nasal cav- 
ity, and lungs. This condition is followed by the develop- 
ment of pustules : these finally give way to dried cells which in 
time loosen and fall off. During the period of eruption the 
patient should be kept in a darkened, well-ventilated room. 
Every precaution should be taken against taking cold. 

Smallpox. — It seems that smallpox originally came from 
Asia and was carried to this country by way of Europe. 
While the disease has long been known and studied by the 
physician, its nature is yet not fully understood. It is 
one of the most highly contagious of all diseases. It may 
be conveyed by contact with the person or clothing of the 
one affected. The cause may linger for years in clothing, 
old trunks, and closets and result in the disease when its 
presence is not suspected. It is probable that the disease 
may be transmitted at any time during its progress, but it 
is usually conveyed to others from the time of eruption 
to the drying up of the so-called scabs. 



BATHING— DISEASES 187 

Generally it takes smallpox twelve to fourteen days to 
develop after the person is exposed. Following this a chill 
usually ushers in a period of three or four days, during 
which the back and the limbs ache and a high fever sets in. 
Four or five days after this, eruption breaks out over the 
skin. Small vesicles or pustules appear which rapidly en- 
large to the size of a pea; small depressions form on the 
top of these pustules giving a characteristic appearance to 
them. These vesicles are filled with a watery fluid which 
gradually turns to a thicker yellowish mass. The temper- 
ature rapidly rises again at this stage, the pustules enlarge 
still further and then break. Finally, they dry up^ form- 
ing dry scabs which drop off, leaving peculiar depressions 
in the skin which give the characteristic pits observed on 
the face of one who has had smallpox. These pits are made 
worse during the progress of the disease by scratching the 
itching portions of the skin. 

While there are some who oppose vaccination, the larger 
number of authorities agree that it is the best prevention of 
smallpox. After the disease has fastened itself upon the sys- 
tem the only thing to be done is to isolate the victim and give 
him the best care possible during the period of the disease. 

It is of interest to note that the dark-skinned races are 
more subject to the ravages of the disease than are the white. 
This may be due in part to the filthy and unsanitary con- 
ditions which sometimes surround the first-named races. 
It is noteworthy also that in some sections smallpox has 
appeared during the last few years in a much milder and 
less fatal form than formerly. It is to be hoped that modern 
science through a better understanding of the causes and 
conditions surrounding the disease may render smallpox 
much less malignant and perhaps entirely eradicate it. 



188 PHYSIOLOGY AND HYGIENE 

Scarlet Fever. — For a long time scarlet fever was con- 
sidered another form of smallpox. Two centuries ago it 
was studied and accurately described; as a result it was 
recognized as a separate and distinct disease, accompanied 
by a high fever, sore throat, and redness of the skin. From 
the time of exposure it usually takes about one week for 
the disease to develop. 

It generally begins with convulsions, vomiting, high tem- 
perature, and quickened pulse. Within twenty-four hours 
eruptions appear about the neck, shoulders, arms, and 
hands, and spread quickly over the whole body. These 
eruptions usually last two or three days, after which they 
begin to disappear. In the worst cases the rash does not 
appear at all. The mouth and throat become red and 
sometimes swollen. 

, After the eruptions disappear, the skin- commences to 
scale off where it is thin; in the thicker places it comes off 
in fragments or pieces. This scaling may continue for 
t>vo , months, during which time the victim is liable to 
complications which are serious in their nature. The in- 
flammation of the throat may extend to the ear, causing 
a discharge from that organ; it may even find its way to 
the brain, with fatal results. The inflammation sometimes 
extends to the eye and results in partial or complete loss 
of vision. Or, inflammation of the kidneys may arise, 
producing a functional disorder of those organs. Other 
organs also may be affected in the same way. 

In every case the patient should be isolated as com- 
pletely as possible, so as to prevent the spread of the 
disease. The room should contain but little furniture 
and should be disinfected every day. After convalescence, 
beds, tables, walls, and clothing should be thoroughly dis- 



BATHING— DISEASES 



189 



infected, toys and other small articles being destroyed. 
Scarlet fever is a serious disease in itself, but it should be 
remembered that many of the complications growing out 
of it are much more to be feared. 

Effects of Alcohol and Narcotics on the Organs of Excre- 
tion. — Alcohol destroys the nerves controlling the blood 
vessels, as a result of which the capillaries of the kidneys 
dilate and the blood surges through these organs. It ab- 
stracts the water from the walls of the uriniferous tubules, 
prevents proper secretion, and subjects the kidneys to 
disease. It produces con- 
gestion of the blood tubes 
of the skin and prevents 
complete excretion of the 
waste matter. Alcohol like- 
wise causes " fatty degenera- 
tion" of the liver. A hard, 
lumpy, irregular structure 
frequently develops in this 
organ, producing the " hob- 
nailed liver." In this con- 
dition the secretion of the 
bile elements cannot take 

place and the elimination of poisonous matter is pre- 
vented. Tobacco tends to deaden the nerve endings in 
the skin. Cigarettes especially have an injurious effect 
upon the skin, leaving it dry and yellow. 




Fig. 79. —Hob-nailed liver. 



CHAPTER XXIII 

THE NERVOUS SYSTEM— THE BRAIN 

Necessity for Perfect Nervous System. — The conditions 
that exist in our modern commercial world are so familiar 
to us that we do not wonder at them. Had our ancestors 
of one hundred years ago been suddenly thrust into the 
industrial life of to-day, they would have been astonished 
and bewildered by their surroundings. 

The regulation of one of our great railroad systems is 
a marvel of modern times. At the head of the system 
are men thoroughly trained and educated in all that per- 
tains to railroading, and out over the country are thousands 
of employees upon whose harmonious action depends the 
successful operation of the railroad. Between the officials 
of the company and the employees is a telegraph system, 
the perfect condition and control of which determines the 
success of the whole system. Let the officials relax or 
fail in performing their duties, and the conditions over 
the entire railroad are paralyzed; let the employees and 
laborers declare a strike or destroy the telegraph wires and 
the results are disastrous to the successful operations of 
the system. 

In the human body the organs of motion, digestion, 
respiration, and excretion may be in a perfect condition, 
but unless there is some central organ of initiation and con- 
trol, and unless the means are present through which this 
control can be exercised, paralysis of the whole system 

190 



THE NERVOUS SYSTEM— THE BRAIN 



191 



will be the result and the various organs will fail to perform 
their functions. That portion of the human body that 
directs and regulates the actions of the different organs is 
the nervous system. 

Nervous Tissue. — The whole nervous system is made up 
of a tissue that is highly specialized. In general, this tissue 
is soft and pliable and contains a great quantity of water. 
The essential parts of nervous matter are the nerve cells 




Fig-. 80. — Nerves in our bodies carry messages as do telegraph wires. 



and nerve fibers; these are bound together by a peculiar 
kind of tissue known as neuroglia. 

Neurons. — As the muscular unit is the sarcomere and 
the lung unit the alveolus, so the nervous unit is the neuron. 
It has just been stated that the essential parts of the 
nervous matter are nerve cells and nerve fibers. The 
neuron is in reality made up of both these structures. 



192 



PHYSIOLOGY AND HYGIENE 




Tig. 81. — Neurons with dendrons. 



A typical neuron is composed of a triangular to irregular 
shaped cell body from which radiate two or three nerve 
branches which may vary in length from a fraction of an 
inch to several feet. 

Not the least interesting features of the neuron are the 

dendrons. These are 
small treelike growths 
of fibrils at the end of 
the larger cell fibers. A 
microscopic study of the 
gray matter of the brain 
shows that this layer is 
largely made up of neu- 
rons. The neurons here 
communicate with each 
other and the spinal cord by means of their fibers, the 
dendrons at the ends of a fiber of one neuron interlacing 
with the dendrons of the fiber of another neuron. While 
these dendrons lie very close together, it is not believed 
that they actually touch each other. Later it will be shown 
how impulses are transmitted from one neuron to another. 
Nerve Fibers. — As we shall have occasion frequently to 
refer to the nerves it may be well to describe these structures 
at this time. Nerves are classified from their appearance 
as white fibers and gray fibers. 

White Fibers. — The larger number of nerves are white; 
these are minute threads of nervous matter about gToT 
of an inch in diameter. They are composed of three 
clearly defined divisions. The inner portion is a slen- 
der, cylindrical thread of gray matter much like the body 
of the neuron cell. On account of its relation to the 
other parts it is called the axis cylinder. Surrounding the 



THE NERVOUS SYSTEM— THE BRAIN 



193 



AX'S CYLINDER 



MEDULLARY SHEATH 



axis cylinder is a mass or layer of white, fatty material 
known as the medullary sheath. Finally, surrounding 
this white coat is a thin, transparent membrane, the 
neurilemma. 

The part that really carries the impulse is the axis cylin- 
der. The medullary sheath serves to protect and nourish 
the delicate axis cylinder within. Its soft, pliable structure 
forms an admirable cushion and support for the frail thread 
within. The color of these fibers is due to the fact that 
the white medullary 
sheath shines through 
the transparent neu- 
rilemma without. 

Gray Fibers.— The 
function of the gray 
fibers is not different 
from that of the white. 
The difference in the 
structure lies in the 
fact that the middle 
coat, the medullary 
sheath, is wanting in 
the gray fibers. Just 
as the color of the 
white fibers is due to the presence of the medullary coat 
under the neurilemma, so the color of the gray fibers is 
caused by the shining of the axis cylinder through the 
outer transparent neurilemma. 

Divisions of the Nervous System. — While the nervous 
mechanism of some of the lower forms of animal life is very 
simple in structure and arrangement, that of the human 
being is very complex and highly specialized. The prin- 



NEURILEMMA 




Fig. 82.— White nerve fiber. 



194 



PHYSIOLOGY AND HYGIENE 



cipal divisions of the human system are the cerebro-spinal 
system and the visceral or sympathetic system. The first 
may, for convenience, be divided into the brain, the spinal 
cord, and the nerves. 

The Brain. — The brain is the central organ of thought, 
initiation, and control. It is a soft, pulpy, elongated 
structure that lies safely imbedded in the cranial cavity of 



CEREBRUM 




PONS VAROLII 
MEDULLA OBLONGATA 



CEREBELLUM, 



Fig-. 83.— Brain, side view, and spinal cord. 

the skull. Its weight varies from ten ounces in the case of 
the idiot, to sixty-five ounces in that of our great thinkers 
and scholars. The ordinary brain of the mature individual 
varies from forty-five to fifty ounces, averaging a little 
higher in the male than in the female. The brain is made 
up of two principal parts, the cerebrum and the cerebellum. 
Between these structures lies the so-called midbrain which 
includes the pons varolii, crura cerebri, and the corpora 
quadrigemina. 



THE NERVOUS SYSTEM— THE BRAIN 



195 



CEREBRUM 



The Cerebrum. — The cerebrum or forebrain occupies the 
upper front portion of the cranium. It constitutes the 
larger part of the whole brain and is by far the most 
important division of that structure. The cerebrum is 
divided into two 
sections or hemi- 
spheres by a deep 
depression, run- 
ning from the front 
to the back, called 
the median fissure. 
Within each hemi- 
sphere is an elon- 
gated cavity or room 
called a ventricle. 

The mass of the 
cerebrum is made 




CEREBELLUM 

Fig. 84 



SPINAL CORD 

Brain, sectional view. 



up largely of white nerve fibers, on account of which fact 
we are often told that the forebrain is composed of white 
matter on the inside. The outside is covered with a layer 
of gray cells or gray matter about one fourth of an inch 
thick. These cells, as has already been stated, have fibers 
extending to each other and to the white fibers beneath. 

The entire surface of the cerebrum is thrown into 
folds or convolutions which give a characteristic ridged 
appearance to the structure. Beginning toward the front 
and outside of each hemisphere a deep depression, known 
as the fissure of Sylvius, extends upward and backward, 
dividing the hemisphere into two principal divisions or 
lobes. The white fibers which make up the inner substance 
of each hemisphere pass downward and unite at the base 
to form one of the branches of the peduncles or crura 



196 



PHYSIOLOGY AND HYGIENE 



cerebri. These two branches unite lower down and extend 
into the medulla oblongata. The two hemispheres are 
bound together by sheets of white tissue called the corpus 
callosum. 

The Cerebellum. — Lying back of and below the cerebrum 
is the hindbrain or cerebellum. This is a much smaller 




Fig-. 85. — Brain, view of base. 
Parts. — a, median fissure; b, pons varolii; c, pituitary body; d, fissure of Sylvius; 

e, crura cerebri; f, spinal bulb; g, cerebellum; h, cerebrum; i, central canal; 

o, infundibulum. 
Nerves. — 1, olfactory; 2, optic; 3, 4, 6, eye motors; 5, trigeminals; 8, auditory; 

9, glosso-pharyngeal; 10, pneumogastric; 11, accessory; 12, hypoglossal. The 

facials lie just above the auditory nerves. 



body than the forebrain and occupies the lower back por- 
tion of the cranium. Here the white matter is found on 
the inside and the gray on the outside. The gray matter is 



THE NERVOUS SYSTEM-^THE BRAIN 197 

so arranged as to give the appearance of a treelike growth. 
The outside of the cerebellum is thrown into a series of 
parallel ridges or folds. 

The Midbrain. 1 — There are other structures that really 
form part of the midbrain besides those mentioned in a 
previous paragraph. They are small, however, and rela- 
tively unimportant, hence will not be discussed here. The 
larger organs are the crura cerebri, the corpora quadri- 
gemina, and the pons varolii. 

The Crura Cerebri. — It has already been said that the 
crura cerebri act as the connecting links between the 
cerebrum and the medulla and, lower down, the spinal cord. 
They are the two cables of white fibers that run from the 
base of each cerebral hemisphere through the medulla to the 
spinal cord and carry impulses to and from the brain. 

The Corpora Quadrigemina. 2 — Between the cerebrum 
and the cerebellum and extending from the back of the 
crura cerebri are four mounds or eminences arranged in 
pairs called the corpora quadrigemina. The function of 

Projecting from the base of the brain immediately back of the 
crossing of the optic nerves, or optic commissure, is a small pear- 
shaped body known as the infundibulum. Fastened to the end of 
this organ is a small brown structure called the pituitary body, the 
function of which is not fully understood. The ancients believed 
that certain portions of waste matter from the worn-out tissues 
called pituita in some mysterious manner found their way to this 
body, from which it passed down into the nose as phlegm. For 
this reason it was called the pituitary body. 

2 An adjacent structure of interest is the pineal gland. This so- 
called gland is nothing more than a small body that lies under the 
back of the cerebrum, in front of the corpora quadrigemina. It is 
supposed by some to be the remnant of an old optic nerve which 
supplied an eye that was once located in the back of the head. 
There is not sufficient proof, however, to make this statement scien- 
tific. 



198 



PHYSIOLOGY AND HYGIENE 



these four bodies is not fully understood, but it is thought 
that they are connected in some way with the sense of sight. 

The Pons Varolii. — This bridge or support is a band 
of connective tissue that folds over the upper part of the 
medulla and holds it to the cerebellum. It has no other 
use than that of holding the different parts of the brain 
together. 

Medulla Oblongata. — The cable of nerves extending 
from the crura cerebri after passing under the pons en- 



PACCHIONIAN BDOV 



DURA MATER 
1 



SUBARACHNOID SPACE AND TISSUE 
SUBDURAL SPACE 
ARACHNOIDEA 




Fig-. 86. — Diagram of brain coverings. 



larges into a bulb which lies just in front of the lower 
edge of the cerebellum. It contains a cavit}^ or ventricle 
which is really an enlargement of the central canal of the 
spinal cord. The medulla may be considered that portion 
of the spinal cord which lies in the cranial cavity. 

Coverings of the Brain. — Spread over the surface of the 
brain are three layers or membranes; the inner one is the 
pia mater, the outer is called the dura mater, while the one 
lying between these two is known as the arachnoid. 



THE NERVOUS SYSTEM— THE BRAIN 199 

The Pia Mater. — This is an extremely delicate membrane 
that closely lines every irregularity of the brain, dipping 
down into each fissure and convolution over the entire 
surface. It contains numerous blood vessels which carry 
material for the nourishment of the brain cells. 

The Dura Mater. — Lining the interior of the cranium 
and surrounding the brain is a tough membrane known 
from its peculiar texture as the dura mater. In addition 
to its use as a wrapping of the brain, it serves as the peri- 
osteum of the cranial bones. It covers the rough portions 
of the bony walls and furnishes a smooth surface to the 
delicate nervous matter within. As its name implies, 
it is a much harder and tougher membrane than the pia 
mater. 

Arachnoid. — Binding the pia mater and the dura mater 
together is a peculiar weblike tissue known as the arachnoid. 
It is a loose, flabby structure composed of threads or 
fibers irregularly woven together. Between the meshes of 
this tissue is a clear, colorless liquid called the cerebro- 
spinal fluid. This liquid bathes all parts of the membrane 
and probably has something to do with its nourishment, 
although its use is not fully understood. 

Functions of the Brain. — The brain is the central organ 
of control of the whole body. In it lies the power to think, 
to feel, and to act. It receives impulses from distant 
parts of the body and sends back counter impulses in 
response. Through the brain all the actions of the body 
are coordinated and movements of the different parts 
harmonized. 

Functions of the Cerebrum. — In the cerebrum lies the 
highest function of the brain. The cerebrum is the seat 
of the thought processes, as perception, conception, reason- 



200 PHYSIOLOGY AND HYGIENE 

ing, memory, and the imagination. It is in the gray cells 
of the cerebrum also that arise the various emotions such 
as joy, grief, happiness, and sorrow, love, hatred, etc. 
It is here, too, that the impulses are stirred up which direct 
and control all these numerous motions and actions which 
make of the human body the most marvelous machine 
known. 

Functions of the Cerebellum. — This structure is essen- 
tially the organ of coordination. If all the impulses sent 
in from distant parts of the body were transmitted to the 
gray cells of the cerebrum and these brought to a state of 
consciousness, the brain would be kept busy in looking after 
our many common movements. Its entire attention would 
be devoted to ' the processes of breathing, digestion, cir- 
culation, excretion, etc. To relieve the cerebrum of this 
detail work other centers are brought into action such as 
those in the spinal cord, medulla, and cerebellum. The 
last-named organ is the seat of control of the voluntary 
muscles. 

While the cerebrum oversees in general the processes 
of walking, running, jumping, etc., the cerebellum controls 
and coordinates the various actions required in these proc- 
esses. For instance, when one runs, certain muscles through- 
out the body are brought into play, and if their actions 
were not harmonized by some central organ the two legs 
would not move in harmony or the arms would not act at 
the proper time and the runner would flounder helplessly 
about without making any progress. It is the duty of the 
cerebellum to see that the muscles are stimulated at the 
right time so that legs, arms, trunk, and other parts per- 
form their individual actions correctly and harmoniously. 
The cerebellum is probably concerned with the control of 



THE NERVOUS SYSTEM— THE BRAIN 201 

other processes besides those connected with the habitual 
motion of the body. 

Functions of the Medulla Oblongata. — The medulla, as 
has been stated, is really nothing more than an enlarged 
portion of. the spinal cord lying within the cranium; in fact, 
it is often called the spinal bulb. It carries the nerve fibers 
from the cerebrum to the spinal cord from whence they 
pass. out to different parts of the body. 

There are, however, certain nerve centers in the medulla 
that control the processes of respiration, circulation, swal- 
lowing, digestion, etc. The medulla is intimately con- 
nected with the control of the organs lying in the thoracic 
and abdominal cavities. Some of the cranial nerves arise 
in this structure. The medulla and cerebellum, with the 
spinal cord, control and harmonize the habitual motions of 
the body and regulate the actions of the heart, stomach, 
intestines, etc. 

Reflex Action. — An important power of the nervous 
system that should be mentioned here is that of reflex 
action. A boy stands by a table on which lies an apple. 
He wants the apple and reaches out his hand to take it. 
In this case an impulse is sent through the optic nerves to 
the cerebrum where a mental picture of the apple is formed. 
As a result of the desire for the apple an impulse is sent to 
the muscles of the arm commanding them to contract, 
which they do, and the boy grasps the apple. This is 
a representative of a large number of sensations that 
reach the cerebrum as a result of which the will decides 
to do a certain thing and impulses are sent out accord- 
ingly. 

There are many impulses, however, as has already been 
said, that never reach the cerebrum and yet are responsible 



202 PHYSIOLOGY AND HYGIENE 

for certain counter or return impulses. I step on a tack ? and 
immediately my foot is withdrawn. A blinding flash of 
light strikes the eye and the lids involuntarily close. The 
foot of the sleeping child is tickled and the muscles contract, 
pulling the foot away. Here the impulses may never reach 
the cerebrum, but stir up cells in some center as the me- 
dulla or spinal cord. These cells immediately send back 
the necessary impulses. This automatic combining of in- 
coming and outgoing impulses is called reflex action. 



CHAPTER XXIV 



THE SPINAL CORD AND NERVES 



PI A MATER 
CENTRAL CANAL 



DURA MATER 

[SENSOR] 
DORSAL 
ROOT 



The Spinal Cord. — The white fibers from the two 
cerebral hemispheres pass downward as the crura cerebri 
and unite to form the medulla oblongata. The medulla 
is constricted at its lower portion where it passes through 
a large opening in the base of the skull known as the foramen 
magnum. While the structure and arrangement of the 
fibers from this 
point on are es- 
sentially the 
same as in the 
medulla, inas- 
much as the 
nervous cable 
penetrates the 
spine almost to 
its lower extrem- 
ity it is called 
the spinal cord. 

The spinal 

cord is about seventeen inches long and three fourths 
of an inch in diameter. It is enlarged slightly in the neck 
and again at a point toward its lower end. It lies safely 
lodged in the neural cavities of the vertebrae. When the ver- 
tebrae are built into the backbone the neural cavities form 

203 




Fig. 87 — Cross section of spinal cord showing- 
coverings. 



204 PHYSIOLOGY AND HYGIENE 

a continuous tube which, with its bony walls, is admirably 
adapted to receive and protect the very delicate spinal cord. 

Branching from the cord are thirty-one pairs of spinal 
nerves. The general shape of the cord is cylindrical. How- 
ever, it has two deep gashes or fissures running down in 
front and behind called the ventral and dorsal fissures. In 
the brain we learned that the white matter is on the inside 
and the gray on the outside; here, however, we find that the 
arrangement is reversed, the white matter being on the 
outside and the gray matter on the inside. The gray 
matter is arranged in a form roughly corresponding to the 
shape of capital H. The four horns of gray matter extend 
almost to the surface of the cord; from the ends of these 
horns spring the branches of the spinal nerves. 

Extending through the center of the cord almost its entire 
length is a small, collapsed tube called the central canal. 
This canal extends into the medulla where it enlarges into a 
good-sized cavity; beyond this cavity it divides into two 
tubes, each of which passes up one branch of the crura cerebri 
and finally opens out into a ventricle of the brain. It will 
be observed that there is a complete connection between 
the ventricles of the cerebrum and the central canal of the 
spinal cord. 

Membranes of the Cord. — The coverings of the cord are 
identical with those of the brain. The tough dura mater is 
on the outside, the delicate pia mater closely envelops the 
cord, and the arachnoid lies between. There is this differ- 
ence to be observed, however : the dura mater of the brain 
serves also as the periosteum of the bone, while that of the 
cord is a separate and distinct membrane, the vertebrae 
having their own periosteum. 

Functions of the Cord. — Often we have observed large 



THE SPINAL CORD AXD XERVES 205 

cables running out from the central station of a telephone 
exchange. These are bundles of wires that transmit 
messages to and from the telephones at the distant ends. 

In the human body the spinal cord takes the place of these 
cables. It carries both sensory and motor impulses. It is 
interesting to note that impulses passing between the brain 
and the distant nerve end organs are not continuous but 
are transmitted successively by several neurons, just as a 
telegram sent from Xew York to Chicago is carried by 
means of several electrical relays. It is probable that as 
many as three or more neurons are concerned in trans- 
mitting some impulses. 

The spinal cord is essentially an organ of reflex action. 
In childhood the brain is called into use in the control of 
all the common movements of the body; gradually different 
centers in the cord take up this work and as they become 
trained in performing these functions the brain is relieved 
of a large part of its former labors, devoting its energy to 
the performance of the higher functions of thinking, know- 
ing, and feeling. 

Experiments show that when the cord is severed all 
sensations arising in those parts of the body beyond the 
break are destroyed. If the sole of the foot be stimulated, 
the limb will jerk in an indefinite way, showing that 
while no sensation or pain has been experienced, an im- 
pulse has been carried to some center in the cord which 
has sent back a counter impulse that produces the jerk- 
ing motion. If the end of the cord next to the brain 
be stimulated, pain is felt, but no motion of the parts 
supplied by the severed cord is observed. Here 'we see, 
then, the reason for believing that the spinal cord is the 
chief center of reflex action. It, in connection with the 



206 



PHYSIOLOGY AND HYGIENE 



medulla, governs those movements and actions of the 
body which result from long-continued practice. 

Nerve Trunks. — We have al- 
ready learned that nerve fibers 
are of two kinds: white and 
gray; that the former is com- 
posed of three coats, the latter 
of two. It may be inferred from 
what has been said in preceding 
paragraphs that every end organ 
has its own particular nerve 
fiber. A little thought will con- 
vince one that it would be im- 
possible for each individual fiber 
to continue its separate course 
from the brain and spinal cord to 
its own end organ. As the thou- 
sands of fibers passing from the 
brain are bound, for convenience 
and safety, into the spinal cord, 
so the hundreds branching from 
the cord are bound, for the same 
reason, into nerve trunks, or, as 
they are usually called, nerves. 
Using the illustration of the tele- 
phone wires again, we may say 
that, as these wires are collected 
into large cables, so the small 
nerve fibers are gathered into 
larger nerve ropes or cables. 
Structure of Nerves. — A microscopic examination of a 
nerve trunk shows that groups of the small fibers are bound 




Fig. 88. — Nerve trunk show- 
ing- divisions. 



THE SPINAL CORD AND NERVES 207 

together into bundles known as funiculi. The connective tis- 
sue that holds the fibers together is called the endoneurium. 
Each funiculus is covered with a membrane, the perineurium ; 
this tissue also binds several funiculi into a nerve or a nerve 
trunk. The whole nerve is covered by the epineurium. 

It will be observed, then, that the ordinary nerve, as we 
see it passing through the tissues of the body, is made up of 
so-called individual fibers, which in turn are composed of 
the extremely small fibers each of which carries impulses 
from the single end organ. Any single nerve contains 
those fibers that supply adjacent portions of the body 
as, for instance, the sciatic nerve is composed of fibers 
that innervate the low T er part of the leg. 

Kinds of Nerves. — There are two kinds of nerves, those 
that carry impulses from the nerve centers out usually to 
the distant end organs, and those that transmit impulses 
from those end organs to the nerve centers. The former are 
called efferent nerves, the latter, afferent. 

Efferent Nerves. — When efferent nerves carry impulses 
that stimulate muscle fibers, producing motion, they are 
called motor nerves. All efferent nerves do not transmit 
motor impulses. For example, certain nerves in the sym- 
pathetic system carry impulses to the blood vessels which 
do not directly produce motion, but which prevent or inhibit 
the action of other nerves. All motor impulses, however, 
are carried by efferent nerves; hence, motor nerves are 
always efferent, but efferent nerves are not always motor. 
The two principal kinds of efferent nerves are those that 
increase the action of a part, the accelerator, and those 
that tend to hinder or impede the action, the inhibitory. 

Afferent Nerves. — The nerves that carry impulses toward 
a center are called afferent nerves. An object coming in 



208 PHYSIOLOGY AND HYGIENE 

contact with a taste bulb of the tongue stimulates the bulb 
and an impulse is transmitted to the brain by means of an 
afferent nerve. An afferent nerve which conveys an im- 
pulse from any of the sensory organs is also a sensory nerve. 
Such are those that give us sensations of light, heat, hearing, 
taste, smell, etc. While all sensory nerves are afferent, 
all afferent nerves are not sensory. Nerves that transmit 
impulses to reflex centers in the ganglia or spinal cord are 
afferent but not sensory. 

Important Nerves. — A study of some of the larger and 
more important nerves is desirable at this time. These, 
as we should expect, spring from the brain and spinal 
cord. They naturally fall into two classes: those that 
arise from the brain within the cranium, called cranial 
nerves, and those that branch from the cord, the spinal 

nerves. 

The Cranial Nerves. — There are twelve pairs of cranial 
nerves, arising from the cerebrum, pons, and medulla. 
These pass out of the cranial cavity and extend to the 
exterior parts of the head and to the vital organs of the 
thorax and abdomen. These are usually known by num- 
ber. They are placed here in the order of their numbers, 
together with their names and locations. 

1. Olfactory Nerves. — The olfactory lobes lie against 
the under side of the front part of the cerebral hemispheres. 
From these lobes the olfactory nerves branch down into 
the nose. They are the nerves of smell. 

2. Optic Nerves. — The two optic nerves rise from the 
base of the cerebrum and extend to the eye. About 
halfway back each optic nerve divides, one half crossing 
to the other side and uniting with a half of the other nerve; 
these two halves on each side pass back as the optic tracts. 



THE SPINAL CORD AND NERVES 



209 



The two halves as they cross over form a single cord called 
the optic commissure. 

3, 4, and 6. Eye Movers or Motor es Oculi. — These regu- 
late the movements of the eyeballs. 

5. Trige?ninals. — These are the nerves of sensation for 
the face and fore part of the head; branches extend to the 




Fig. 89. —Cranial nerves. 



tongue and teeth. The branch running to the front of the 
tongue is the gustatory nerve, supposed by some to be a 
nerve of taste. 

7. Facials. — These control the muscles of the face and 
determine the expression of the same. 

8. Auditory Nerves. — These pass to the internal ear 
and are the nerves of hearing. 



210 PHYSIOLOGY AND HYGIENE 

9. Glossopharyngeals. — The ninth pair of nerves in- 
nervate the base of the tongue and the walls of the pharynx; 
they are the nerves of taste. 

10. Vagi or Pneumogastric Nerves. — The vagi send 
branches to the lungs, stomach, heart, larynx, and to other 
structures, including the sympathetic system. 

11. Spinal Accessory Nerves. — These arise close to the 
point where the spinal cord leaves the cranium. They 
supply the muscles of the neck. 

12. Hypoglossals. — As the name implies, these control 
the action of the tongue. 

Spinal Nerves. — There are thirty-one pairs of spinal 
nerves; these rise from the spinal cord. Each nerve con- 
nects with the cord by two branches or roots. The one 
toward the front is the ventral; the one toward the back is 
the dorsal. As the ventral root carries motor impulses, it 
is frequently called the motor root; similarly, since the 
dorsal root transmits sensory impulses, it is called the 
sensory root. 

Each dorsal or sensory root has a ganglion located at a 
point close to its juncture with the motor root. The sen- 
sory roots spring from the dorsal horns of gray matter 
already described as lying in the cord. In a like manner 
the motor roots rise from the ventral horns. In both cases 
the branches pass out through the white matter of the cord 
and, uniting, emerge from the neural ring through small 
openings between the vertebrae. From this arrangement 
it will be observed that incoming or sensory impulses pass 
through the dorsal roots, while outgoing or motor impulses 
pass through the ventral roots. 

The ganglion of the dorsal root is supposed to strengthen 
in some way the sensations passing through it. By some 



THE SPINAL CORD AND NERVES 211 

it is believed that the ganglion nourishes the cells and 
coverings of the nerve. 

Functions of the Spinal Nerves. — Each pair of spinal 
nerves innervates portions of the viscera, muscles, skin, 
and other tissues lying below their connection with the 
cord. They carry ordinary sensations and counter impulses 
of reflex action producing motion. 

The Sympathetic System. — Arranged on each side of the 
backbone is a row or chain of twenty-four ganglia. These 
with the ganglia of the opposite side constitute the twenty- 
four pairs of the sympathetic system. 

It might be added that an extra large median ganglion 
connected with these at the lower end close to the coccyx 
is really a part of the system. These ganglia send out 
branches to the viscera, to one another, and to the spinal 
cord. The ganglia at the upper end of the chain send 
branches directly to the base of the brain. It will be ob- 
served, then, that the sympathetic system is connected 
with the brain by two routes, through the cord and through 
the branches from the upper ganglia. 

Functions of the Sympathetic System. — As has been 
stated, branches pass from the ganglia of this system to 
the different vital organs of the trunk. Impulses carried 
through these nerves control the actions of these organs, 
regulating the processes of digestion, respiration, circula- 
tion, etc. 

It has been suggested that the expression " sympathetic 
system " is a misnomer; that, inasmuch as this system con- 
trols the viscera, it should be called the visceral system. 
The use of the former expression probably resulted from the 
fact that the processes mentioned above are sometimes 
affected by certain states of the mind, as fear, grief, sor- 



212 



PHYSIOLOGY AXD HYGIENE 



GANGLIA OF 
SYMPATHETIC 
SYSTEM 



SACRAL PLEXUS 




PNEUMOGASTRIC NERVE 



CARDIAC PLEXUS 






SOLAR PLEXUS 



AORTIC PLEXUS 



MESENTERIC PLEXUS 



Fig-. 90. — Ganglia of sympathetic system. 

row, anger, etc. It is a well-known fact that fear will in- 
fluence the action of the lungs and heart, while grief and 
sorrow affect the appetite. Under a normal condition of 




THE SPINAL CORD AND NERVES 213 

the mind the sympathetic system regularly controls the 
actions of all the abdominal and thoracic organs, as stated 
above. 

Ganglia. — The term ganglion has been used several 
times and it may not be out of place at this time to explain 
more fully what it is. A ganglion is a collection of gray 
cells through which passes a single nerve or from which 
radiate a number of 
nerves. These ganglia 
may lie alone or they 
may be collected into 
groups closely connected 
with each other. The 
ganglia found on the pos- 
terior roots Of the spinal Fig , 91. -Ganglion and nerves, 
nerves have already been 

mentioned, as have those that make up the two chains 
of the sympathetic system. Others are found in various 
r^arts of -the body, especially in the abdominal and tho- 
racic regions. 

Plexuses. — Occasionally we find a collection of ganglia 
connected by a network of nerves. Such a collection with 
the accompanying ganglia is called a plexus. One of the 
largest of these nerve meshes is the solar plexus which lies 
immediately back of the stomach. Branches pass from it 
to various structures of that region, but particularly to the 
muscle fibers of the lungs. Another large plexus is situ- 
ated just above the heart; this is called the cardiac plexus. 
Two other important plexuses are located, one close to the 
aorta, the other in the upper part of the arm, and are called 
from their positions the aortic plexus and the brachial 
plexus. The plexus of Meissner lies in the submucous coat 



214 



PHYSIOLOGY AND HYGIENE 



of the stomach and other parts of the alimentary canal and 
innervates the walls of these structures. 

Stimuli. — We have learned that there are two kinds of 
nerves : those that carry impulses away from the center and 
those that carry them toward the same. Whichever way 
these impulses travel, they must have something to start 

them; the something is 
called a stimulus. The 
cause of all stimuli can- 
not be explained. A few 
of the most important 
will be mentioned here. 
Mechanical Stimuli. — 
Impulses may be set up 
in nerves in a mechani- 
cal way, as by a pinch, 
a tap, or a blow. The 
skin of the arm is 
pinched and an impulse 
is started which upon 
reaching the brain pro- 
duces pain. A blow or 
a tap is administered 
to some part of the 
body with a similar 
result. 

Thermal Stimuli. — These are produced by a change of 
temperature. A warm object comes in contact with the 
skin and an impulse arises in a nerve which ends at this 
point. Likewise a cold object starts an impulse which is 
transmitted to the proper center. 

Chemical Stimuli — Soluble substances coming in con- 




Fig. 92. — Plexus, 



THE SPINAL CORD AND NERVES 215 

tact with the tongue give rise to sensations of taste. Ex- 
tremely fine portions of matter striking the cells in the 
mucous membrane of the nose stir up impulses which are 
interpreted at the center as smell. This kind of stimulus is 
supposed to be due to a chemical cause. 

Electrical Stimuli. — If the handles of a galvanic battery 
be held in the hands while the machine is in action the 
muscles are stimulated and the arms tremble. If electricity 
be applied to the nerves in a frog's leg the muscles violently 
contract. 

Light Waves. — When the retina of the eye receives rays 
of light, impulses are started, which, upon reaching the 
proper center, give rise to sensations of sight. 

Sound Waves. — Vibrations, set up in the air, upon reach- 
ing the inner ear start impulses which give rise to sensations 
of hearing. 

Other Kinds of Stimuli. — Impulses traversing the nerves 
are started in other ways besides those mentioned above. 
When food is thrown into the stomach impulses are sent to 
the proper center calling for an increased flow of the blood 
to the gastric glands. After the stomach has been empty 
for some time, impulses are sent to the brain demanding 
food. The mind wills to do something and an impulse is 
stirred up which upon being transmitted to the proper part 
produces the desired effect. Impulses are developed in 
other ways besides the ones mentioned, depending for their 
origin upon some peculiar state or condition of the body. 



CHAPTER XXV 

HABIT— HYGIENE 

Habits. — In a previous paragraph it was stated that, 
through reflex action, various functions of the body are 
performed automatically; that is, without the direct over- 
sight of the brain. The ordinary actions of the body are 
performed without any conscious effort. The child, when a 
baby, moves about by crawling or creeping. When a little 
older, with the aid of a chair or the assistance of the parents, 
it is able to walk in a very awkward and clumsy fashion. 
In the earlier stages of walking each step is the result of a 
mental effort on the part of the child. After its legs have 
become sufficiently strong and it has taken many steps, the 
process becomes automatic. 

Many others of our every-day acts are controlled, not by a 
conscious effort of the cerebrum, but by the lower centers 
of the medulla and spinal cord. This tendency to do 
automatically those things that have been done over and 
over again is called habit. 

Correct Habits. — Some one has well said that char- 
acter is a bundle of habits. This statement suggests the 
fact that we form habits that govern our thought processes 
as well as habits that control our physical actions and 
motions. The formation of habits of both kinds is some- 
thing that cannot be avoided. It is one of the provisions of 
nature that habits be formed and it depends upon each of 
us as to whether these shall be good or bad. 

216 



HABIT— HYGIENE 217 

If we desire to develop a body that is dignified in its bear- 
ing and graceful in its actions we must begin while young 
to train our muscles to act harmoniously as well as 
promptly. The boy who shuffles about in a loose, care- 
less manner is bound to develop into an awkward man. 
Young people who stoop continuously over their desks 
need not be surprised to find later that they are possessed 
of round shoulders and sunken breasts which affect both 
the health and the comeliness of the body. Boys and 
girls cannot lounge at the table or loll in the parlor and 
develop those traits and qualities peculiar to gentlemen 
and ladies. 

We have all heard the story of the bent sapling. 
"WTien it grew into a tree its trunk was crooked and gnarled, 
presenting a very unsightly appearance. Workmen were 
called in and told to straighten the trunk, but try as hard 
as they could it resisted all their efforts, remaining bent 
and twisted to the end. Had the sapling been given at- 
tention when it was young and pliable it could have been 
straightened and perhaps might have grown into a grace- 
ful, symmetrical giant of the forest. If we desire to possess 
a comely, well-rounded, attractive body when old, we must 
be careful, patient, and persistent in our efforts to form 
right habits while we are young. 

Habits of Thought. — We are told that our thoughts 
•shine out through our countenances, giving them expression 
of coarseness, refinement, criminality, sincerity, treachery, 
or honesty. When we meet new faces we judge their char- 
acter largely by the expression of the features. Since this 
is true, how necessary it is that we avoid evil and degrading 
thoughts. 

It is just as easy to form bad habits of thinking as 



218 PHYSIOLOGY AND HYGIENE 

it is bad habits of walking or sitting. If we wish to pos- 
sess frank, open, honest features, we must get into the 
habit of thinking only pure and noble thoughts. The 
development of the various faculties of the mind such as 
the imagination, memory, perception, etc., depends largely 
on the formation of correct habits of thinking. The one 
who falls into the habit of studying a lesson or reading a 
book without the proper concentration of the thought proc- 
esses will soon lose the power to focus his mental faculties 
upon the subject at hand. As a result he will ordinarily 
be unable to grasp the full meaning of a difficult lesson, or ? 
if he does, he will not be able to remember it. 

Complete mastery of a subject comes only from giving it 
our undivided attention. The pupil who permits his mind 
to wander while reading or studying will finally discover 
that, no matter how much he may try, he can no longer 
concentrate the powers of his mind upon any given object 
of thought. It might be said here, too, that young people 
should early form the habit of observing carefully those 
things that come before their attention. The ability to see 
rapidly the many details of objects with which one comes 
in contact is an evidence of a well-trained mind. Parents 
and teachers should insist that the boys and girls form such 
mental habits as will later make them strong intellectually 
and at the same time sincere, honest, high-minded men 
and women. 

Hygiene of the Nervous System. — We have learned how 
necessary it is that every bone, muscle, and tissue of the 
body about which we have studied should be kept in good 
order if we desire to get the most out of our physical being. 
We are now to learn that it is just as important to guard, 
well the delicate structure of the nervous system. The 



HABIT— HYGIENE 219 

heart, lungs, digestive and other organs may be in perfect 
condition, but unless the nerve centers and fibers that 
control them are able to perform their duties properly the 
action of the other organs will be impaired. The muscles 
of the arm may be fully developed, but unless impulses of 
sufficient intensity and coordination are transmitted to 
these muscles, the arm is useless. To understand fully 
the hygienic conditions that govern the proper action of 
the whole body it is necessary to consider the supply of 
fresh air and pure blood, exercise, rest, and sleep. 

Fresh Air and Pure Blood. 1 — It must be remembered that 
without fresh air we cannot long have pure blood and with- 
out pure blood the rebuilding of worn-out tissues is im- 
possible. Nervous matter must be nourished just as any 
other tissue is. If the supply of oxygen is cut off, the nerve 
cells and fibers cannot be replaced and the initiation or 
transmission of impulses is rendered impossible. 

The effect of shutting off the supply of fresh air is 
observed in the crowded assembly hall where all windows 
and doors are tightly closed. Both the people who com- 
pose the audience and the lights that illuminate the hall 
consume oxygen and give off carbon dioxide. As a result, 
the blood cannot get oxygen, the tissues cannot be rebuilt, 
the nervous system can no longer originate impulses nor 
transmit them, and the people become drowsy and perhaps 

J A curious arrangement for supplying blood to the brain is ob- 
served in the circle of Willis. This is a circular tube something 
like an inflated bicycle tire lying at the base of the brain. Branches 
from the carotid arteries open into it on each side, supplying; it from 
two directions. If the blood should be cut off from on a side by 
the rupture of one of the carotids it could still enter the circle of 
Willis from the other. This adjustment practically assures a con- 
tinuous flow of blood to the brain. 



220 PHYSIOLOGY AND HYGIENE 

go to sleep. The same effect is noticed in sitting rooms 
and bedrooms where the ventilation is not good. 

Many persons who naturally have weak systems are 
subject to fainting spells under conditions of this kind. 
Even if the blood is pure, unless an abundant supply is 
carried to the brain and nerves, these organs cannot act 
normally. As suggested at another place, nature has fur- 
nished the brain with a sufficient number of blood vessels 
to nourish it, but often conditions prevent a full supply 
of blood to this organ. 

When the body is in an upright position, gravity tends 
to draw the blood away from the head; when the body is 
lying down a greater quantity of blood moves to the brain. 
This explains two interesting facts. When a person faints 
he is laid out on a floor or couch; the blood rushing to the 
head distends the arteries and veins of the brain and the in- 
dividual returns to consciousness. Often one grows sleepy 
as he sits up in his chair in the evening while reading and 
decides that he must retire. Upon getting into bed the 
blood supply to the brain increases to such an extent that 
he cannot go to sleep, but tosses about as a result of wake- 
fulness. This accounts for the fact that many difficult 
problems that cannot be solved while the individual is 
sitting up are easily worked out after he goes to bed. 
Those who wish quick, active brains and a prompt response 
on the part of the muscular system must make provision 
for a sufficient quantity of oxygen in the blood and an 
abundant supply of blood to the brain. 

Exercise and the Nervous System. — Often when one is 
weary and nervous from long-continued mental exertion, 
the brain may be nourished and the mind rendered more 
active by exercise. This permits of a cessation of mental 



HABIT— HYGIENE 221 

labor and at the same time of a revitalization of the blood. 
Muscular exertion in the fresh air increases respiration 
and provides for the intake of oxygen through the lungs 
and the elimination of waste matter through all of the 
organs of excretion. The purified blood is sent whirling 
through the capillaries of both muscles and brain and all 
of the tissues of the body are once more built up. The 
nervous system has had time to recuperate and the un- 
finished mental labor may now be resumed and completed 
with vigor and dispatch. 

Rest. — We have discussed the matter of fatigue that 
follows prolonged muscular effort. But even more notice- 
able is the mental fatigue that succeeds extended in- 
tellectual activity. How weary and depressed we feel after 
several hours of hard, uninterrupted study. How often 
are tired, nervous students compelled to drive their flagging 
minds to continued mental efforts when it seems that they 
have lost all control over them. Change is one of the laws 
of nature. We tire of performing the same labors, doing 
the same things, and viewing the same scenes from day to 
day. How much the monotony of life is varied by a 
change of the surroundings and scenery. Change is rest 
in both the physical and intellectual worlds. When, as a 
result of continued mental application, our faculties fail to 
respond to our efforts it is time to give them rest. A walk 
up a shady avenue, a ramble through a cool wood, an hour 
spent in the garden, or even a few minutes engaged in 
some innocent amusement, will permit the mind to relax 
and as a result we will be able to return to our studies 
with renewed physical and intellectual vigor. 

Sleep. — In this age of hurry and haste it is doubtful 
whether many of us would take time to rest if nature did 



222 PHYSIOLOGY AND HYGIENE 

not force us to it. In these times when the electric arc light 
changes night into day, our tendency to live rapidly and 
achieve much might impel us to work unceasingly through 
the whole twenty-four hours of the day, were it not for the 
fact that the demands of nature decree it otherwise. 

The daytime was made for labor and the night for sleep 
and rest. During this cessation from both physical and 
mental labor it is possible for body and mind quietly to 
repair the worn-out tissues and strengthen the weakened 
faculties. Many thoughtless persons do not give proper 
attention to the matter of sleep. They keep late hours, 
retiring after midnight, thus robbing themselves of sleep 
which is so necessary to the preservation and health of their 
bodies. 

Everyone should have regular sleeping hours. Chil- 
dren should be permitted to sleep from ten to twelve 
hours, sometimes longer. Adults may find six to eight 
hours sufficient. Instances have been known where great 
writers and thinkers have rarely slept more than four or five 
hours daily, often less. While these persons may get along 
with this amount of sleep, in time the whole system begins 
to show the effect and a complete physical and mental break- 
down is the result. 

Many people are troubled with wakefulness after retiring 
for the night. Various remedies have been suggested for 
overcoming this sleeplessness. However, the real cure lies 
in putting the body and mind in such a condition that sleep 
follows naturally. As far as possible worry should be 
banished and cares forgotten. Vigorous exercise in the 
evening, or just preceding retirement, usually brings sleep. 
After all, the mental states are very closely related to the 
physical conditions. If we keep the body in a strong, 



HABIT— HYGIENE 223 

healthy condition, the mind can be better kept under control 
and refreshing sleep made possible. 

Alcohol and the Nervous System. — The injurious effects 
of alcohol on the nervous system are due largely to the 
affinity that the narcotic has for water. The nerves are 
rendered hard and incapable of transmitting impulses 
properly. The brain cells are likewise hardened and when 
once broken down cannot be repaired; as a result, a con- 
dition arises known as " softening of the brain." This 
condition leads to results discussed under the subject of 
stimulants and narcotics. The nerves being paralyzed, 
the arteries are distended with blood, the walls become 
weak and often burst, producing apoplexy. 

Tobacco and the Nervous System. — Like alcohol, tobacco 
deadens the nerves and hardens the cells of the brain. 
The mental and moral effects are discussed under the 
subject of narcotics. 



CHAPTER XXVI 

THE SENSES— TOUCH 

Necessity for Senses. — We have made a study of the 
skeleton, of the muscles, of the circulation, of the organs 
of digestion, of the nervous system, and of all those tissues 
and structures that go to make of the body a perfect 
physical mechanism. We have learned how the brain is 
the seat of thought, feeling, and action, and how it is con- 
nected by nerves with all parts of the body. It remains 
to be seen how this brain, this mass of nervous matter, 
comes to know the great outside world, how it receives 
impressions from this world, and how it controls the many 
movements and actions which mean so much to the human 
being. 

We need but to imagine that the brain is cut off from 
all communication with the external world to conceive of 
the utter helplessness of the human structure in its efforts 
to develop and perform those functions for which it was 
created. But nature never does anything by halves. 
When man was created and endowed with a knowing and 
thinking mind, his physical structure was so developed 
and specialized that this mind was placed in direct com- 
munication with the world without. The means .through 
which this communication is carried on are the senses. 

Sensations. — It is desirable here to discuss briefly what 
we mean by sensations. When a ray of light strikes the 
eye, or a sound wave the ear, when an object touches the 

224 



THE SENSES— TOUCH 225 

hand, when food comes in contact with the tongue and odors 
strike the organs of smell, impulses are stirred up and sent 
to the brain where they are interpreted as something par- 
ticular and special; these are called sensations. 

It may be observed that there are three parts to every 
sensation of this kind. There is first a stimulation of the 
specialized end organ lying at the distant extremity of 
the nerve; second, the transmission of the aroused im- 
pulse by the nerve; finally, the interpretation of the impulse 
in the brain. These kinds of sensations are called special 
sensations. There are sensations of another kind that 
arise wholly within the body known as general sensa- 
tions. Some of these are hunger, thirst, fatigue, and 
weariness. 

Pain. — A peculiar kind of sensation that is neither 
special nor general is pain. When any nerve is stimulated 
beyond a given limit it ceases to perform its ordinary 
function and carries to the brain a signal of alarm. This 
signal, which produces a more or less disagreeable im- 
pression upon the brain center, is a manifestation of pain. 

If we press lightly upon a portion of the body we ex- 
perience the sensation of touch, but if the pressure is in- 
creased beyond a certain point the impression of touch dies 
away and a feeling of pain arises. So it is in the case of the 
eye. If rays of light enter that organ and strike the retina, 
an impulse is conveyed to the brain which is appreciated 
as sight. But if the light be intense* or long continued, the 
sensation of sight gives way to pain. 

Pain is one of nature's means of protecting and pre- 
serving the body. Were it not for pain the hand would 
be burned to a crisp on the hot stove, the delicate linings 
of the eye would be destroyed before the blaze of the sun. 



226 PHYSIOLOGY AND HYGIENE 

the teeth would rot and drop from their sockets, and the 
body would soon be covered with unsightly wounds and 
scars. Pain is the one vigilant sentinel that is ever on the 
alert to guard the body against disaster. 

Special Senses. — The lower the animal is in the scale of 
life the fewer organs it requires to perform the functions 
necessary to its existence. The higher it rises in this scale 
the more complicated is its structure and the greater variety 
of organs it needs for its development. The amoeba uses 
the same portion of the body as a skin, a foot, and a stomach. 
In man, where the organ is highly organized, every function 
has its own particular organ. For digestion, we find the 
stomach and intestines; for excretion, we find the kidneys, 
skin, and lungs, and for the mind, we find the brain. 

For the purpose of conveying impressions of the external 
world to the brain, man might have been supplied with a 
single kind of end organ. But the impressions and sen- 
sations thus carried to the brain centers w r ould be very in- 
complete and indefinite indeed. 

To the end that the mind might receive vivid impres- 
sions and clear-cut sensations of all that goes on in the 
external world about it, the body has been supplied with 
a particular kind of organ for every form of sensation. 
For receiving sensations of roughness and smoothness we 
have the sense of touch; for determining the condition of 
bodies with respect to heat and cold we have the sense of 
temperature; for recognizing flavors and odors we have 
the sense of taste and the sense of smell, and for receiving 
sensations from sound and light waves we have the sense 
of hearing and the sense of sight. In addition to these we 
have the so-called sense by means of which we get impres- 
sions of resistance and weight. 



THE SENSES— TOUCH 



227 



Touch. — The skin over the entire body contains nerve 
endings that are sensitive to the touch. The impressions 
produced by objects coming in contact with the body are 
carried to the brain. That these impressions may rise to 
the highest degree of sensitiveness they must be received 
by certain specialized structures called end organs. There 
are a number of these end organs, but the most important 
ones are: Pacinian corpuscles, tactile cells, end bulbs, and 
touch corpuscles. 

Pacinian Corpuscles. — These are the largest of the end 
organs, being about one tenth of an inch long. Their 
great size makes it possible for them 
to be seen with the naked eye. They 
are found at various places throughout 
the body, but are particularly plentiful 
in the areolar tissue under the skin of 
the hands and feet. They are composed 
of concentric layers of connective tissue 
surrounding the enlarged extremities 
of the nerves. While the Pacinian cor- 
puscles are the largest end organs they 
are comparatively few in number and 
are relatively unimportant as organs of 
touch. 

Tactile Cells. — An examination of the epidermis shows 
that some of the cells in the lower part surround the small 
nerve fibers which extend slightly above the dermis. 
These specialized cells are end organs of touch and are called 
tactile cells. While they do not play as important a part 
in the sense of touch as some of the other structures, they 
are undoubtedly concerned in receiving impressions that 
are definite and well defined. 




NERVE 



Fig. 93. — Pacinian 
corpuscle. 



228 



PHYSIOLOGY AND HYGIENE 




Tig. 94. 



Dermal papillae with touch 
corpuscles. 



Touch Corpuscles. — The most highly specialized end 
organs of touch are the touch corpuscles. When the dermis 

was discussed it was 
stated that the surface of 
this layer of skin is not 
smooth, but covered 
with rows of small papil- 
lse each of which con- 
tains a mass of nervous 
matter connected with 
the nerves. These nerve 
masses are the touch cor- 
puscles. A touch cor- 
puscle is about one three- 
hundredths of an inch 
in length and one five-hundredths of an inch in thickness. 
Sometimes as many as two or three nerve fibrils are con- 
nected with a single corpuscle. The touch corpuscles are 
found all over the body, 
but are especially numer- 
ous on the fingers, toes, 
lips, and tongue. The 
palm of the hand and sole 
of the foot are well sup- 
plied with them. Here 
may be found as many 
as fifteen thousand to 
the square inch. 

End Bulbs.— Although 
the existence of these 




Fig. 95.— End bulhs of eye. 



structures is generally conceded by the scientists, all do not 
agree as to their arrangement and function. It has been 



THE SENSES— TOUCH 229 

proved that they exist on the tongue, lips, and in or on the 
conjunctiva of the eye. There is no doubt that end bulbs lie 
in the outer layer of the lips and the tongue. Whether or 
not they lie in the conjunctiva or project from this mem- 
brane has not been definitely proved, although the best 
authorities believe that they are minute globular structures 
that float in the tears, suspended from the ends of nerve 
fibers that project from the conjunctiva. The extreme 
sensitiveness of the eye is probably due to the fact that 
foreign bodies, lodging in the eye, become entangled with 
the end bulbs and their nerves, producing great pain. In a 
sense the end bulbs are not organs of touch, but are present, 
at least in the eye, to notify the brain of the presence of 
particles that are liable to injure the organs. 

Sensitiveness of Different Parts of the Body. — It is 
possible to determine the sensitiveness of the skin by 
finding the least distance at which the ends of a compass 
appear as two distinct points. By this method it has been 
proved that the most sensitive parts of the body to the 
touch are the lips, tongue, and finger tips. The compass 
points applied at a considerable distance apart to the cheek 
or the middle of the back give the impression of a single 
point, but if they are brought to the tongue or the tips of 
the finger, the distance between the points being main- 
tained, two distinct impressions are received. It may be 
that use has made certain parts of the body more sensitive 
than others. This suggests the thought that the sense of 
touch may be cultivated. 

Education of the Sense of Touch. — Without doubt, 
delicacy of touch may be inherited, but we have many 
illustrations about us of the fact that this sense may 
be rendered keener and more sensitive by practice. The 



230 



PHYSIOLOGY AND HYGIENE 



skilled pianist strikes several keys accurately in a single 
second, the bank cashier detects a counterfeit by the deft 
sweep of the hand, the merchant determines the grade of a 
piece of goods by crushing it between his fingers, and the 
surgeon locates, by his practiced touch, an abscess deep 
within the body. 

Dr. A. R. Taylor says in his " Study of the Child": "The 
extent to which touch is cultivated in some of the schools 
for defectives, is shown in the skill with which the blind and 
the deaf read raised letters in English and German. Su- 
perintendent Hammond states that Helen Keller gets the 
thought of a friend by placing her fingers on his lips and her 
thumb on his throat as he speaks. At the World's Fair 
she visited the art gallery, and, after passing her hand over 
the head and face of several pieces of statuary, said of one, 
'This face feels sad.' It was the statue of Melancholy. 
She seems to have brain cells in her finger tips. More 
recently Miss Keller has said, 'How can the world be 
shriveled when this most profound emotional sense, touch, 
is faithful to its service ? I am sure that, if a fairy bade 
me choose between the sense of sight and that of touch, I 
would not part with the warm, endearing contact of human 
hands or the wealth of form, the nobility and fullness 
that press into my palms.' The cases of Helen Keller 
and other defectives show what can be done in educating 
the senses, particularly that of touch. This education, 
however, should begin while the child is young, when the 
organs are delicate and the mind especially susceptible to 
impressions." 

Deception in the Sense of Touch. — When end organs 
lying in parts of the body are stimulated we come to ap- 
preciate the resulting sensations as coming from those 



THE SENSES— TOUCH 



231 



particular parts. If the stimulation is applied on the finger 
we know the sensation as coming from that part, if applied 
on the neck we recognize the sensation as coming from that 




Fig. 96. —With the fingers crossed the pupils think that 
they are touching- two pencils. 

locality. By experience we know at once what part of the 
body has been touched. 

Curiously enough, this very fact leads to deception. 
Pupils are frequently asked to cross the first and second 
fingers and then place a pencil between them so that it will 
touch the outside of the fingers, when almost invariably 
the pupils think that they are touching two pencils, espe- 
cially if they close their eyes or look in the opposite 
direction. 

Cases are on record in which it is stated that wounds on 
the face have been partially covered with skin that had 
been, in part, removed from an uninjured portion. After 
the wounds have healed over, if the transplanted skin be 
touched the sensation appears to arise in the place from 
which the skin has been taken. In one instance a strip 
of skin from the forehead was engrafted on the nose; 
when this part of the nose was touched the sensation 
seemed to originate in the forehead. 



232 PHYSIOLOGY AND HYGIENE 

Another peculiar kind of deception which is of interest 
in this connection is observed in the case of the individual 
who loses a limb by amputation. Often the stimulation 
of the nerve stump causes sensations that appear to come 
from some part of the amputated limb. 

Functions of the Sense of Touch. — Touch may in a way 
be considered the lowest in the order of senses, yet it is one 
of the most important. Hearing and sight give us pleasur- 
able feelings and agreeable impressions that add materially 
to the enjoyment of life. The eye presents to the mind the 
green forests, the blue skies, the pleasant fields, beautiful 
pictures, and faces of our friends. The ear conveys to the 
mind the agreeable sounds of nature, the voices of our com- 
panions, and the melodies and harmonies of music. 

The other senses contribute in a greater or lesser degree 
to our enjoyment, but touch is the servant of them all. 
It gives us ideas of smoothness, hardness, roughness, and 
sharpness. Indirectly it gives us impressions of extension 
and solidity. It assists the eye in forming correct ideas of 
size, shape, and distance. It aids the ear in judging as 
to the cause of particular sounds, as the rasping of a 
file. It helps the sense of taste in determining whether 
food taken into the mouth is proper or improper. 

To quote from Dr. Taylor again: "It is essential to the 
protection of all parts of the body against injury, and, like 
the sense of temperature, is more sensitive in parts that 
are more susceptible to harm. It immediately reveals the 
presence of insects and vermin of every description; of 
objects coming against it, whether sharp or dull, rough or 
smooth, hard or soft; and too great pressure or constriction 
of any part of the clothing. What miserable creatures we 
should be if compelled to wait for a fly to bite or a mosquito 



THE SENSES— TOUCH 233 

to fill his nib before knowing of his presence! Think of 
the suffering which would everywhere ensue if we could 
know nothing of a rough substance until continual rub- 
bing against it had produced rawness or inflammation 
of the skin." 



CHAPTER XXVII 

TEMPERATURE, MUSCULAR SENSE, TASTE, SMELL 

Sense of Temperature. — It was once thought that the 
ability to appreciate changes of temperature is dependent 
upon the sense of touch, but it is now quite certain that this 
ability is due to the presence in the skin of distinct tempera- 
ture nerves. It has been successfully shown that there are 
small areas or points on the skin around nerve endings 
which if stimulated give rise only to sensations of warmth. 
Similarly, there are areas surrounding other nerve endings 
which give rise only to cold sensations upon being stimu- 
lated. It is supposed that the entire body is covered 
alternately with these points and that when a warm object 
comes in contact with the skin only one kind of area 
responds. In the same way the other kind will respond 
only to cold objects. The first areas are known as warm 
points, while the other areas are called cold points. 

Function of the Sense of Temperature. — But little is 
learned concerning the external world through this sense. 
Its function is much like that of touch in that it protects 
the body from danger. Immediately upon the body's 
coming in contact with or near objects extremely hot or 
cold, it notifies the central organ, and the body or the part 
affected is removed from danger. Were it not for this 
sense the end organs of touch would have to be stimulated 
to such a degree that pain would result before the brain 
could be notified of impending danger. Even then serious 

234 



TEMPERATURE, MUSCULAR SENSE, TASTE, SMELL 235 

injury might result from burning or freezing before the body 
could be removed from the cause. In addition this sense 
keeps the centers fully informed as to the condition of the 
surrounding atmosphere. Without the sense of temper- 
ature the body might be fairly comfortable and yet the air 
be so hot or cold that all of its functions could not be 
performed properly. 

Education of the Sense of Temperature. — From the very 
nature of this sense it is not very susceptible to education. 
It is true that experience teaches the housewife to know- 
when the oven is ready for the bread by merely putting her 
hand in the oven and the physician to determine the degree 
of fever by applying his hand to the patient's brow. The 
conclusions drawn by these persons are more dependent 
upon reasoning and comparison than upon the training of 
this sense. 

The Muscular Sense. — Another sense formerly supposed 
to be dependent upon or closely allied with touch is the 
so-called muscular sense. That this is not a true sense is 
shown by the fact that it does not have its own special end 
organs. Inasmuch as it gives us certain definite ideas of the 
external world — ideas that could be furnished in no other 
way, it is usually classed with the senses. The muscular 
sense gives us ideas of resistance, tension, and especially 
weight and the location of the different parts of the body. 

Functions of the Muscular Sense. — A heavy bucket 
hangs in a well suspended by a rope; we determine the 
tension in the rope by moving it back and forth with the 
hand. We desire to find out how heavy a loaded cart is; 
we push it and the resistance it offers to the push indicates 
something of the load. We wish to know the weight of a 
block of wood or a ball of iron and we lift it several times 



236 



PHYSIOLOGY AND HYGIENE 







with the whole arm. We desire to touch some particular 
part of the body with the finger; the peculiar tension of the 
muscles indicates the location of the part and the hand 
easily finds the place. As stated above, the muscular 
sense aids us in determining resistance, tension, weight, 
and location of the different parts of the body. 

Education of the Muscular Sense. — The butcher and 
the merchant can tell quite well in advance the weight of a 

piece of meat or a package of 
sugar. The ball player knows just 
how hard to strike a ball of given 
weight. A person can determine 
very accurately the weight of an 
object by "hefting" it several 
times in the hand. The boy can 
close his eyes and bring his finger 
within half an inch of his nose or 
ear without touching it. 

The power to do these things 
comes only from long experience, and the knowledge gained 
in this way is valuable. How helpless we would be without 
the ability to estimate fairly well the weight of the many com- 
mon objects about us. The child, as it takes its first lessons 
in eating, applies quite as much of the food to its chin and 
cheeks and eyes as it does to its mouth. Experience, how- 
ever, teaches it to bring the food to its mouth with ease, 
grace, and accuracy. How inconvenient it would be in 
making his toilet, if one were compelled to pass his hand 
promiscuously over the body in order to button his coat, 
adjust his tie, comb his hair, or lace his shoes. A person 
would be helpless in the extreme were it not for the 
muscular sense and the power to train it. 



mt'mk 



Fig. 97. —Papillae of 
tongue. 



TEMPERATURE, MUSCULAR SENSE, TASTE, SMELL 237 



Taste. — The membranes lining the interior of the mouth 
are the seat of three senses : touch, temperature, and taste. 
While sensations of taste arise at various places in the 
mouth, the largest number come from the surface of the 
tongue. In the description of this organ on another page 
it was stated that the surface of the tongue is covered with 
three kinds of papillae, the circumvallate, fungiform, and 
filiform. The first two of these are concerned with the 
sense of taste, the filiform papilla? serving as organs of 
touch. Formerly it was 



PAPILLA 



TASTE BULBS 



thought that "the branches 
of the nerve ending in the 
mucous membrane of the 
tongue were the seat of taste 
sensations, but during the 
latter part of the last century 
it w r as shown that the sense 
is due more largely to the 
presence of minute nervous 
structures lodged in the tis- 
sue of the fungiform and 
circumvallate papilla?. 

Taste Bulbs. — These are 
small goblet-shaped nervous 
masses lying in the walls of the papilla? mentioned above. 
They are about one three-hundred ths of an inch in length and 
less in breadth. The taste bulbs are rarely found at the 
top of the papilla?, but come to the surface at the sides or 
base of these projections. While a great many are observed 
toward the front part of the tongue, the largest number 
occur on the back of that structure, particularly in the region 
about the circumvallate papilla?. Here several hundred are 




iV/A,".; \y 

Tig. 98.— Taste bulbs. 



238 PHYSIOLOGY AND HYGIENE 

probably to be found in a single papilla. The taste bulbs 
are bathed in the saliva at their outer extremities and are 
connected with branches of the glossopharyngeal nerve 
within. 

Nerve Fibers. — While the taste bulbs are essentially the 
organs of taste, many small, branched nerve fibers in the 
tongue come to the surface and receive sensations of taste. 
These nerve fibers are found largely on the front part of the 
tongue. However, they are unimportant when compared 
with the taste bulbs. 

Nature of Taste. — Insoluble substances cannot be tasted. 
Only those that dissolve upon coming in contact with the 
tongue can affect the sense of taste. Materials like clean 
sand, pebbles, and nails, etc., have no taste when put in the 
mouth. Dry sugar and salt when placed upon the parched 
tongue cannot be tasted; it is only when they are dissolved 
by the saliva and brought into contact with the end organs of 
taste in the soluble form that their presence is appreciated. 

Kinds of Taste. — Taste may be classified as bitter, 
sweet, acid, and saline. Other so-called tastes can realty 
be placed under one of these four. Sweet tastes can most 
readily be appreciated at the front of the tongue. Bitter 
and salty substances are most easily recognized at the base 
of the tongue. 

Use of Taste. — The sense of taste was placed in the 
mouth to assist us in the selection of food. In general 
the food that is obnoxious to the taste is unfit for the 
stomach and that which is agreeable to the taste is that 
which the system requires. Often food that looks appetiz- 
ing is unfit for use, and this fact is determined by the taste 
when the food is taken into the mouth. Moreover, taste 
undoubtedly adds to our enjoyment directly. This is 



TEMPERATURE, MUSCULAR SENSE, TASTE, SMELL 239 

evident from the fact that practically all of our "soft 
drinks" are consumed because of their taste rather than 
their cooling qualities. 

Education of Taste. — The sense of taste is subject to a 
moderate degree of education. Small children do not make 
the distinction between sweet and sour substances that older 
ones do. Foods that were distasteful to us when we were 
young we now relish. Some people come to like celery or 
olives only after they have used them for a long time. The 
experienced housewife judges of the character of the food 
largely by the taste. Salesmen for large tea houses have 
the sense so highly developed that they can pick out cer- 
tain kinds of tea from a large number submitted. In a 
great many cases, however, taste is influenced by the 
other senses, particularly that of smell. 

Smell. — The sense of smell bears the same relation to 
the air conveyed through the nasal cavities that the sense 
of taste does toward food taken into the mouth. The seat 
of this sense is in the upper part of the membranes lin- 
ing the nasal cavities and covering the turbinated bones. 
Lying in these membranes are specialized cells, to the 
presence of which are due sensations of smell. 

Olfactory Cells. — We have already learned that the 
windpipe is lined with several layers of cells, the inner of 
which stand perpendicular to the surface and possess small 
fine hairs or cilia at the inner extremity. These ciliated 
structures are likewise found in the upper membranes of 
the nasal cavities. 

Scattered among these are elongated specialized cells 
that project slightly above the others; these are olfactory 
cells. Each one is connected with a fiber from the olfac- 
tory nerve. The olfactory nerves extend forward under 



240 



PHYSIOLOGY AND HYGIENE 




the front of the cerebrum and end in the large olfactory 
bulbs. From these bulbs extend numerous branches 

through the sievelike bone be- 
neath and spread out over the 
mucous membrane, connecting, 
as indicated above, with the 
olfactory cells. 

How We Detect Odors. — Be- 
fore anything can be tasted it 
must be dissolved, likewise be- 
fore anything can be smelled it 
must be changed to the vapor 
or gaseous condition. When a 
rose is brought near the nose 
extremely small particles de- 
tach themselves, enter the nos- 
trils, and come in contact with 
the olfactory cells. It seems that the condition of smell- 
ing is that the mucous membrane be moist. The mucus 
secreted by the membrane is usually sufficient to keep 
the cells moist. Often, as in the case of a severe cold, the 
membranes become hard and dry and the ability to ap- 
preciate odors is much lessened. 

The sense of smell is rendered much more acute by 
drawing the air rapidly through the nostrils. Hence when 
one wishes to satisfy himself thoroughly concerning any 
particular odor he " sniffs" the air into the nose. It is a 
well-known fact that if one breathes a fragrance into the 
nasal cavities and then holds the nose shut with the hand, 
the olfactory cells are no longer affected by the odor. 

Keenness of the Sense. — Smell is a comparatively unim- 
portant sense in man. In the lower animals, however, it is 



NERVE T | i! P|Ffi 

Tig. 99. — Olfactory cells. 



TEMPERATURE, MUSCULAR SENSE, TASTE, SMELL 241 

very highly developed. It would seem that it reaches its 
fullest development in animals that exist in water. The 
presence of objects that give out odors can be detected 
by these animals at a great distance. It is well to state, 
though, that it is difficult to tell whether this faculty is a 
result of smell 1 or taste, as these two senses are so closely 
related in these animals. 

It hardly need be suggested that the sense of smell is 
highly developed in such animals as the dog, the wolf, the 
deer, and other like animals. In these it is the means of 
eluding enemies and acquiring food. It is also keen in 
certain savage races and is used for the same purpose as 
in the case of the lower animals. It is stated on good 
authority that the sense of smell is very sensitive in blind 
and deaf persons; instances have been mentioned where 
such people have been able to recognize individuals by the 
sense of smell alone. 

1 The senses of taste and smell are so closely connected that we 
often confuse one with another. What may appear as an odor to 
one person might be considered a taste by another. Many claim 
that the so-called taste of the onion is in reality an odor. To prove 
this claim, they assert that if a person close his eyes and hold his 
nose, and pieces of onion and apple be placed on his tongue, he 
cannot tell the difference, provided they are of like texture. 



CHAPTER XXVIII 



HEARING 



OSSICLES 

CONCHA 
SEMICIRCULAR CANAL 
AUDITORY NERVE 
VESTIBULE 



Hearing. — The sense of hearing lies in the ear. This 
is an organ that is very complex in its structure. In many 
of the lower animals the ear is very simple in its arrange- 
ment, being merely the small cavity in which is suspended 
a sac containing a fluid. In some cases the ear does not 

open out on the 
surface. The 
higher the animal 
is in the scale of 
life the more com- 
plicated the hear- 
ing apparatus. In 
man there are two 
ears, one on each 
side of the head. 
The human ear 
includes three di- 
visions; the ex- 
ternal ear, the 
middle ear, and 
the internal ear. 

The External 

Ear. — This part 

of the ear lies at the lower side of the head and is itself 

composed of two parts, the concha and the auditory 

. 242 




COCHLE 
EUSTACHIAN TUBE 

TVMPANIC MEMBRANE" 

UTRICLE 

MEATUS 



Fig-. 100. — Mechanism of the ear. 



HEARING 



243 



meatus. The concha is a curiously shaped structure made 
up of yellow elastic cartilage. It is especially tough and 
strong, yet so pliable that it bends before a severe blow 
and does not break as it would were it made of bone, 
and does not easily tear loose as it might were it made of 
ordinary connective tissue. 

It is funnel-shaped and grooved in order more easily to 
catch sound waves that are carried in its direction. Ex- 
tending from the front toward the back is a small fold of 
cartilage that closes the auditory meatus when struck with 
a sharp instrument; this arrangement protects the middle 
ear from injury. 

The auditory meatus is the canal that leads into the 
interior. It is a tube less than one half inch in diameter 
and about one inch long. Coarse hairs grow from its walls 
and slant toward the concha so 
that, while it is difficult for in- 
sects to get into the ear, it is 
easy for them to get out. Large 
sebaceous glands secrete a 
thick, yellow, waxy secretion 
that keeps the membranes soft 
and assists in killing bugs and 
insects that crawl into the 
canal. 

The Middle Ear. — This is a 
cavity connecting the outer and 
inner divisions of the ear. It 
is separated from the external 
ear by the thin, delicate tympanic membrane. On ac- 
count of its similarity to a drum the middle ear is fre- 
quently called the tympanum. It is an irregular cavity 



INCUS 



MALLEUS 




STAPES 

MEMBRANA TYMPANl 

Fig-. 101.— Middle ear with 
chain of bones. 



244 PHYSIOLOGY AND HYGIENE" 

about one fourth of an inch in diameter. The tympanum 
is lined with mucous membrane and with the exception of 
the small bones mentioned below contains nothing but 
air. It lies in the mastoid process, a bony knob which 
may be felt just back of the ear. The middle and ex- 
ternal ears are both surrounded by the so-called petrous 
bone, the hardest osseous tissue in the body. By prying 
with a knife under the tympanic bulla of the rabbit it will 
come off and both the tympanic membrane and the 
tympanum will be exposed. 

Ear Bones. — Stretching from the tym- 
stirrup P amc membrane to the oblong opening or 
oval foramen of the vestibule is a chain 
of three bones: the malleus, incus, and 
stapes. These names mean hammer, 
anvil, and stirrup, and are so called from 
their resemblance to these articles. The 
handle of the hammer is fastened to the center of the tym- 
panic membrane and the body articulates with the anvil. 
This last bone connects with the stirrup, the base of which 
covers the oval foramen. These bones are extremely small, 
but are bound by their own ligaments and are controlled 
by their own muscles. The muscle that is attached to the 
stapes is the smallest in the whole body, being only about 
one sixth of an inch long. 

Eustachian Tube. — Extending downward and inward 
from the middle ear to the back part of the mouth is a canal 
about one inch and a half long called the Eustachian tube. 
It is lined with mucous membrane throughout its entire 
length. 

The function of the Eustachian tube is to allow an 
equalization of the air pressure on both sides of the 





HEARING 245 

tympanic membrane. It is well known that the pressure 

of the atmosphere varies from day to day. Were there no 

arrangement by means of which the pressure could be 

equalized on the tw r o sides of 

the tympanic membrane this ggjjpjgygVEs-nBuu 

delicate structure would be 

placed under different degrees 

of tension, as a result of rods =^^^^M^P^$cala 

' OF CORTI I 1 TYMPAN* 

which the sound wave could 

, . inn Fig. 103. — Section of cochlea. 

not be conveyed equally well 

at all times. Not only could we not hear as well all the time, 
but a violent explosion of a gun or peal of thunder might 
actually burst the membrane, producing absolute deafness. 
The Eustachian tube, by permitting air to pass through, 
provides for the constant tension of the tympanic membrane. 

The Internal Ear. — The inner mechanism of hearing, 
which includes the vestibule, cochlea, and the semicircular 
canals, is called the internal ear. The various winding 
tubes of these three structures are collectively known as 
the labyrinth. 

Osseous Labyrinth. — The different tubes and cavities 
of the internal ear, excavated in the petrous bone, compose 
the bony labyrinth. The cavities throughout are lined with 
a membrane and filled with a limpid fluid called the peri- 
lymph. 

The Membranous Labyrinth. — Floating in the peri- 
lymph is an elongated and closed sac or tube filled with a 
liquid otherwise known as the endolymph. This is the 
membranous labyrinth which follows quite regularly the 
windings of the bony labyrinth. Branches of the auditory 
nerve are distributed to the membranous walls of this 
structure. 




246 PHYSIOLOGY AND HYGIENE 

The Vestibule. — Lying between the semicircular canal 
and the cochlea and articulating with the tympanum 
through the oval foramen is an antechamber known as the 
vestibule. It contains an enlarged portion of the mem- 
branous tube or labyrinth, which, as stated above, passes 
from the semicircular canals to the cochlea. A membrane 
stretched across the oval foramen, against which rests the 

stirrup, keeps the perilymph 
from passing into the tympa- 
num. The function of the ves- 
tibule is to receive sound waves 
through the oval foramen and 
%sterior canal pass them on b} T means of the 
104.-C0cM.ea and vesti- perilymph to the cochlea. 

bule of the ear. l m L 

The Cochlea. — This is a shell- 
like excavation made in the bone. It winds spirally two 
and a half times to the apex and contains three membran- 
ous tubes lying side by side. These tubes are part of the 
membranous labyrinth and contain the liquids before men- 
tioned. In the middle tube is found the delicate mechanism 
of hearing. Stretched across the floor of this are about 
three thousand strings. Standing on these strings are two 
rows of rods arranged something like the rafters of a house; 
these are the rods of Corti. The strings and rods are con- 
nected with the end of the auditory nerve and receive im- 
pressions that produce sensations of sound. One of the 
other tubes transmits the sound waves from the vestibule 
to the apex of the cochlea. The wave is then carried across 
to the other tube which conveys it down and out into the 
tympanum. It is while the sound wave comes down this 
last tube that it affects the end organs of hearing. 

How Sound Reaches the Ear. — When a gun is discharged 



HEARING 247 

at a distance we see the puff of smoke and soon hear the 
report of the gun. When a locomotive whistles we first 
observe the steam rushing out and soon hear the sound of 
the whistle. If a workman strikes a barbed wire or a 
telephone wire the ear may hear the sound of the hammer 
through the wire as much as one half mile away. Boys in 
swimming discover that by cracking two hard objects to- 
gether under the water, the sound produced can be heard 
quite a distance if the ear be held under the water also. In 
these cases, the air, the wire, and the water carry the sound 
from its origin to the ear. 

If a bell were struck without a medium between it and 
the ear it would be impossible for the sound to reach that 
organ; in other words the ear could not hear it no matter 
how close it might be. Almost all sounds that reach the 
ear are carried through the air. When a sounding body 
is struck it vibrates and throws the air also into wavelike 
motions. These vibrations pass out through the air much 
as waves move away when a pebble is thrown into the 
water. There is a difference, however; the water waves 
are circular while the air waves are spherical. The sound 
waves passing through the air are caught by the concha 
and cast into the auditory canal. 

The Sound Wave in the Ear. — As indicated in the pre- 
ceding paragraph, the sound wave is received by the 
concha and thrown into the meatus, through which it is 
carried to the tympanic membrane. Striking this organ, 
the vibration is transmitted to the chain of bones by means 
of which it is carried to the oval foramen. It is here taken 
up by the perilymph of the vestibule and conveyed through 
one of the tubes mentioned above to the apex of the cochlea, 
where it is cast into the other tube. Passing down through 



248 PHYSIOLOGY AND HYGIENE 

the perilymph of this tube the sound wave beats up against 
the strings stimulating the rods of Corti, after which it is 
carried on down to the tympanum ; where it is finally lost 
in the air that fills that organ. 

Functions of the Semicircular Canals. — While these 
canals are without doubt intimately concerned in the 
matter of hearing, yet they have other functions of even 
greater importance. It has long been known that they 
are connected in some way with the power of the body to 
maintain its equilibrium. It may be observed that the 
three canals are placed at right angles to each other so that, 
no matter in what direction the head is turned, it must 
move in general along one of the planes in which lie the 
canals. We have already learned that these tubes are 
filled with perilymph and endolymph. It has been sug- 
gested that when the head is quickly turned in any direc- 
tion these liquids, on account of their inertia, are left 
behind, much as water in a bucket tends to stand still 
when the bucket is quickly rotated in the hand. In the 
same way if the head be turned many times in succes- 
sion the liquids in the canals will finally take on the 
motion of the head just as the water takes on the motion 
of the bucket after it has been rotated a number of times 
in succession. 

We shall be able to understand this better if we study the 
case of children who whirl around and around until they 
fall down from dizziness. They whirl their bodies so often 
that the canal liquids finally move with the head. When 
the head is suddenly stopped the liquid continues to move 
through the canal, giving the impression that the body is 
still in motion. It will be seen, then, that the slightest 
motion of the head will produce a movement of these 



HEARING 249 

liquids. By these sensations the body is enabled to main- 
tain its equilibrium and retain its upright position. 

Diseased Conditions of the Ear. — The hearing in many 
persons is naturally defective, but defects are in some 
cases brought on by conditions which might be controlled. 
Anything that tends to produce a sudden change of temper- 
ature in or about the ear is liable to lead to a more or less 
disordered condition of the hearing apparatus. An inflam- 
mation from a severe cold in the head may extend up 
through the Eustachian tube to the tympanic membrane, 
materially interfering with the functions of that organ. 
Scarlet fever often "settles " in the ear, leading to a perma- 
nent derangement of the different parts of the mechanism. 
A violent explosion or heavy blow on the head is liable to 
result in the rupture of the ear drum and a consequent 
" breaking ' J or "running" of the ear. 

Defective Hearing Common. — A careful investigation 
will reveal the fact that many persons are defective in 
hearing who are not aware of the fact. Many pupils 
in the lower grades of our public schools have impaired 
organs of hearing. Too often children are punished for 
inattention or failure to perform a certain task when the 
difficulty lies in the fact that they are partially deaf. The 
writer has come in contact with cases of this kind in his 
work as city superintendent. Boys have been whipped 
severely because, apparently, they would not listen to 
what the teacher was saying. Girls have been scolded and 
kept in during intermission because they failed to obey 
some of the commands of the instructor. 

A little skillful questioning has shown that these boys 
and girls have been heedless and listless not because they 
were lazy, but because they could not hear. Is there any- 



250 PHYSIOLOGY AND HYGIENE 

thing more pathetic than a child that strains every nerve 
of its body in its efforts to catch the words as they fall 
from the lips of the teacher and finally gives up in despair 
because it cannot hear? But the pitiful thing about the 
whole matter is the fact that neither the pupil nor the 
teacher has the slightest conception of the difficulty. 
Careful experiments have shown that fully half of the 
boys and girls in some of our schoolrooms are defective 
in hearing. One of the first duties of the teacher is to 
determine who the defectives are and to deal with them 
accordingly. 

Hygiene of the Ears. — As suggested above, many defects 
grow out of conditions that could have been avoided. The 
hair around the ears should not be left wet, especially during 
cold weather. In cleaning the auditory meatus one ought 
to use tepid water and afterwards the canal should be wiped 
dry. The earwax ought not to be permitted to accumulate 
and harden, but should be removed by warm water or an 
instrument with a round, smooth end. Insects which get 
into the ear may be killed by warm water or oil and then 
washed out. Loud explosions or sudden noises close to the 
ear should be avoided. The thoughtful parent or teacher 
will never strike the child on the head. Undoubtedly 
many cases of partial deafness have been caused by pro- 
miscuous boxing about or on the ears. 

Instruments to Relieve Deafness. — When the delicate 
organs of hearing are not completely destroyed but only 
defective they may be assisted in performing their functions 
by artificial means. Many elderly persons increase their 
power to hear by placing the curved hand back of the ear; 
in this way more sound waves are thrown into the canal. 
Where the hearing is very defective, buglelike instruments, 



HEARING 251 

with wide, flaring mouths, called ear trumpets, are used to 
intensify the sound waves. In case the mechanism of the 
middle and external ears is completely destroyed, deafness 
may be counteracted by the use of an instrument known as 
the audiphone. This consists of a thin sheet of metal or 
diaphragm especially contrived to fit between the teeth. 
The sound waves are received by this and transmitted 
through the teeth and bones to the internal ear. 



CHAPTER XXIX 



SIGHT 



The Sense of Sight. — The eye is one of the most 
marvelous structures in the human body. Sight is the 
highest in the order of the senses. By it we get our ideas 
of shape, distance, size, color, etc., of the various objects 
scattered about us. The man who has been blind from 
infancy knows but little or nothing of the wide prairies, 
broad seas, lofty mountains, blue skies, and friendly faces 
that mean so much to the one who sees. Even the insects 
around us have the power of seeing their food or observing 
their enemies. Practically all kinds of animal life have 
special end organs in which the power of vision is developed 
to a greater or lesser extent. 

Kinds of Eyes. — Scientists have discovered three kinds 
of eyes in different animals. These are: eye 
specks or eye dots, compound eyes, and the 
simple or ordinary eye of the human being 
and other higher animals. 

Eye specks are expansions of the optic 

nerve that lie just under a transparent 

layer or membrane through which the light 

passes. Having no refracting medium, this 

kind of eye gives rise only to sensations 

of light, no image whatever being formed. 

Fig.i05.-ZZn Impressions from these eyes are very much 

of a compound like tllose rece i V ed by closing the lids of 

cyc» 

252 




SIGHT 



253 



CHRYMAL GLAND 



our eyes and looking toward the sun. Compound eyes 
are made up of a number of inverted transparent cones. 
The apex of each cone is connected directly with a filament 
from the optic nerve. The field of vision is not very large, 
but acuteness is secured. The fly has a compound eye. 
The simple eye is made up of a number of refracting 
media inclosed in a hollow ball. The human eye is an 
illustration of the simple eye. 

The External Eye. — The real organ of sight is the eye- 
ball. However, when we speak of the eye we usually refer 
to the ball and those external structures associated with 
it, such as the eyebrows, 
eyelids, and eyelashes. 
These are symmetrically 
arranged so as to permit upper and lower 

° A LACHRYMAL DUCf! 

of the most perfect vision 
and at the same time give 
expression to the features. 

The Eyebrows. — Lying 
at the upper angle of the 
eye socket and at the 
lower edge of the forehead 
on each side are the eyebrows. These consist of folds 
of integument and tufts of hair pressed close to the skin 
and pointing outward and downward in such a way that 
perspiration descending from above is carried to the side of 
the face rather than into the eyes. The eyebrows in some 
cases, by projecting over the eye, protect this organ from 
intense light. Moreover, the row of hairs is gracefully 
arched so as to give beauty to the face. 

The Eyelids. — The eyeball is curtained in front by two 
movable sheets of skin and connective tissue called eyelids. 




NASO-LACHRYMAL DUCT 

Fig. 106.— Eye, external. 



254 PHYSIOLOGY AND HYGIENE 

These sheets are curved to fit the eyeball perfectly and 
contain thin bands of cartilage which help the lids to keep 
their shape. The lids are lined on the under side by a 
mucous membrane called the conjunctiva. This is a very 
delicate lining from which project the end bulbs mentioned 
in discussing the sense of touch as being so sensitive. 

Surrounding the lids is a circular or sphincter muscle 
which contracts and closes the eye. Each lid is fringed 
along its free edge with a row of hairs which meets the 
row on the other side when both are closed. These are the 
eyelashes, and their texture, length, color, and curvature 
have a great deal to do with the beauty of the eye. 

Scattered between the roots of these hairs along the edge 
of the lid are large secretory organs known as the Meibo- 
mian glands; they secrete an oil which lubricates the edge 
of the lids and prevents the ordinary secretion of the 
tears from running over the lid and down the face. 

The functions of the eyelids and lashes are to regulate 
the amount of light which enters the eye, puevent foreign 
particles from injuring the cornea, protect the eye from 
sudden changes of temperature, distribute the tear to 
all parts of the eye properly, and add beauty to the 
features. 

The Lachrymal Apparatus. — The lachrymal gland oc- 
cupies a depression in the outer edge of the eyebrow. The 
tear secreted by this gland is conveyed to the under side 
of the upper lid by six or eight ducts which pour the tear 
slowly out between the lid and the ball. A peculiar motion 
of the lids in winking works the secretion across the front 
of the eye to the inner angle. Here it soaks through a 
small opening into the lachrymal canal, and finally through 
the nasal duct into the nose. 



SIGHT 



255 



During crying or irritation of the eye the secretion is 
excessive and flows out over the edge of the lids as tears. 
The fact that the tear sometimes reaches the nose is proved 
by the saline taste of the fluid that gets into the mouth 
when one cries. The function of the tear is to keep the 
eyeball moist and clean. 

The Eyeball. — As has been stated, the real mechanism of 
sight is the globe of the eye or the eyeball. This is a sphe- 
roidal structure 

i , i • LEVATOR PALPEBR/C SUPERIORS 

about one men in 

,. . i • "I SUPERIOR OBLIQUE 

diameter which SUPERI0R REcm 
rests in a cushion optic nerve 
of adipose tissue, 
the whole being 
lodged in a deep 
bony cavity called 
the eye socket. 
Imbedded in 
this socket, and 
protected by the 
tough eyelids and 
overhanging eye- 
brows, the eye is 
with good vision. 




INTERNAL RECTUS 



EXTERNAL RECTUS 
INFERIOR OBLIQUE 
INFERIOR RECTUS 



Fig-. 107. — Eyeball and muscles. 



in as safe a location as is consistent 
The ball itself is composed of a strong, 
tough external wall within which is to be found the 
several structures that are concerned with the matter of 
vision. 

The Sclerotic Coat. — While the wall of the eye is com- 
posed of three coats, the strength mentioned above is due to 
the presence of the external layer which is called in the 
back part of the eye the sclerotic. It is composed of tough 
white fibrous connective tissue which is stiff enough to 



256 PHYSIOLOGY AND HYGIENE 

maintain the shape of the eye. That the strength of this 
coat in the beef eye is very great is proved by the fact that 
it will bear the weight of a man without bursting. Through 
the sclerotic at the back part of the eye passes the optic 
nerve and blood vessels. 

In the front of the eye the white sclerotic is continued 
as the tough, transparent cornea. A portion of the 
sclerotic may be seen around the clear, colorless cornea 
as the white of the eye. To the sclerotic are fastened six 
muscles which control the movements of the eye. 

The Choroid Coat. — A very thin, delicate layer closely 
attached to the interior of the sclerotic is called the choroid. 
It is made up largely of color pigments and contains many 
small capillaries and blood vessels. Anyone who lias 
examined the interior of a camera or kodak remembers that 
it is painted black; this is done in order that all extra rays 
of light may be absorbed, making it possible for a distinct 
image to be formed. In a like manner and for the same 
reason the pigment cells line the inner surface of the 
sclerotic coat as the choroid. 

At the point where the sclerotic changes to the cornea, 
the choroid gives way to the colored curtain which hangs 
down in front of the crystalline lens as the iris. This curtain 
has a round opening at its center known as the pupil 
through which the rays of light enter the eye. Plain 
muscle fibers, which lie in the iris both circularly and 
radially, by contracting, make the pupil larger or smaller as 
the case may be. While the color pigments in the choroid 
are black, those in the iris are varied in color. As a result 
we have persons with different colored eyes; some black, 
some blue, some gray, the color depending upon the color 
pigments in the iris. In albinos all of the color pigments 



SIGHT 257 

are wanting, consequently their eyes are white or pink. 
The function of the iris is to increase or decrease the size 
of the pupil, hence to regulate the amount of light that 
enters the eye. 

The Retina. — The optic nerve enters the back of the 
eye, almost directly opposite the pupil. Immediately upon 
entering it spreads out over the interior of the eye as the 
retina. It will be observed then that the retina is in reality 
the expansion of the optic nerve. It is thickest where the 
optic nerve enters and gradually grows thinner toward the 
place where the choroid meets the iris. Here it fades away 
entirely. 

The retina is a sensitive transparent membrane that 
adheres closely to the choroid at every point. Under the 
microscope the retina appears to be made up of eight or 
ten fairly distinct layers. In one of these layers lie the 
so-called rods and cones; peculiar-shaped rod or clublike 
structures that are parallel to each other and perpendicular 
to the surface of the retina. These rods and cones in some 
way receive the impressions of light and pass them on 
to the optic nerve through which they finally reach the 
brain. 

The Optic Mound and Yellow Spot. — As the optic nerve 
enters the eye, its fibers heave up into a mound just before 
they spread out as the retina. This mound is not sensitive 
to light and is known as the optic mound or blind spot 
inasmuch as a distinct image cannot be formed at this place. 
Not far from the blind spot and directly behind the pupil 
in the path of direct vision is a depression in the retina 
known as the yellow spot. In the center of the depres- 
sion or pit thus formed is the point of acutest vision in 
the eye, called the fovea. 



258 



PHYSIOLOGY AND HYGIENE 



The Humors of the Eye. — When the eye first develops 
in the human being it contains many veins, arteries, and 
capillaries. These convey to the interior of the ball an 
albuminous liquid which is deposited to such an extent that 
the eye is not only filled but distended by the excess of the 
fluid. After the ball is once crowded full with this liquid 
the blood vessels begin to disappear, actually devouring 
themselves. The liquid deposited is separated into three 
divisions, each of which develops into a humor having a 
special function. 
■ The liquid which fills the front part of the eye is called 

the aqueous hu- 
_sclerotic mor. It is bound- 
ed in front by the 
cornea and in the 
rear by the iris and 
pupil. It, serves 
as a transparent 
medium for the 
transmission o f 
light and, by keep- 
ing the cornea dis- 
tended, makes it 



CILIARY MUSCLE 



CHOROID 




AQUEOUS, 

HUMOR 



"Fig, 108. — Eye, cross section. 

It takes its name from the fact that 



lustrous and bright 
it is thin and watery. 

The rear and main portion of the eyeball is filled with 
a thicker glassy liquid called the vitreous humor. It 
is bounded in front by the crystalline lens and ciliary 
process; at the sides and back it touches the walls of the 
eye. It keeps the ball distended and at the same time 
permits the light to pass through to the retina. Behind 
the pupil and in front of the vitreous humor is the crystalline 



SIGHT 259 

lens filled with a humor much like the vitreous. Its func- 
tion is to transmit and bend the rays of light so that they 
may be brought to a focus on the retina, forming an 
image. 

Hyaloid Membrane. — In addition to the three coats 
already mentioned as forming the wall of the eye, there is a 
membrane lying within the retina and inclosing the vitreous 
humor, known as the hyaloid membrane. This is a thin, 
transparent tissue that follows the wall closely to the front 
of the vitreous cavity where it extends in behind the iris. 
The front portion of the hyaloid membrane is split into two 
layers between which is located the crystalline lens. The 
hyaloid membrane is so arranged that under the influence 
of the ciliary muscles it regulates the shape of the lens and 
the length of the eye, thus providing for the formation of 
distinct images. 

The Crystalline Lens. — We have already learned some- 
thing about the crystalline lens. If we were to take a 
spherical portion of gelatine about one half inch in diameter 
and press it gently between the fingers until it were some- 
what' flattened, we would have a structure not unlike, in 
shape and appearance, the crystalline lens. It is convex on 
both sides and is shaped something like a burning glass. 

It is located immediately back of the pupil and, being 
convex, bends the rays of light, bringing them to a focus on 
the retina. Before the eye can see it is necessary that rays 
be brought to a focus and an image formed. Without the 
crystalline lens this could not be done. The lens is held in 
place by the two layers of the hyaloid membrane men- 
tioned above. The portion of the membrane where it 
splits or divides to surround the lens is called the suspensory 
ligament. 



260 PHYSIOLOGY AND HYGIENE 

The Muscles of Accommodation. — Just outside of the 
suspensory ligament is found a mass of plain muscle fibers 
that act on the hyaloid membrane to focus the eye; this is 
the ciliary muscle. It has already been stated that plain 
muscle fibers lie in the iris, running both circularly and 
radially. When the circular fibers contract the pupil de- 
creases in size; when the radial fibers contract, the pupil 
enlarges. Certain drugs, notably belladonna, when applied 
to the eye cause the pupil to dilate. Others cause it to 
contract. 

How We See. — We have learned that sound waves 
usually get to the ear through the air. Light waves are 
not carried by the air, but are transmitted through a very 
rare medium which is supposed to occupy all space; this 
medium is the ether. Light waves move through the ether 
with a speed of about 186,000 miles per second. 

WTienever a body gets hot enough to glow, it gives out 
vibrations which reach the retina of the eye and give us the 
sensation of light. The sun is extremely hot and sends out 
myriads of light waves which move through the ether. 
Some of these waves come to the earth, enter the eye, and 
give rise to impressions of light. Others of these waves 
strike bodies about us and are reflected into the eye. These 
rays seem to originate in the objects themselves and 
entering the eye they affect the expanded optic nerve 
and we get sensations of the size, shape, color, and general 
appearance of the objects. 

The formation of images on the retina is due, as has been 
stated before, to the presence of the crystalline lens. With- 
out this lens the eye would be able to give us mere sensa- 
tions of light, but no clear-cut images. If a lamp be 
placed before an eye from which the lens has been removed 



SIGHT 261 

the eye would see the light but would receive no image of 
the flame, chimney, or lamp. The lens not only permits 
rays of light from any object to pass through, but also 




Fig. 109. — Diagram showing how image is formed in eye. 

brings these rays to a focus on the retina. The image thus 
formed is taken up by the optic nerve and carried to the 
brain where it is appreciated as a house, a man, or a horse, 
as the case may be. 

A peculiar thing about these images is that they are in- 
verted when formed on the retina, but as all objects around 
us are inverted at the same time, we do not notice the 
inversion. Anyone who has ever examined a kodak has 
noticed a lens at the front end. If one were to place a 
ground glass at the proper place at the rear of the kodak 
and turn the instrument toward some particular object he 
would see an inverted image of the object on the ground 
glass. Not only would the image be inverted but it would 
be much smaller than the object. The fact is, the eye 
is very much like the kodak; the crystalline lens in the 
former represents the glass lens in the latter and the retina 
takes the place of the ground glass 

How the Eye is Focused. — Experience teaches us that a 
kodak will not take a photograph in which objects, both 



262 



PHYSIOLOGY AND HYGIENE 



CILIARY MUSCLE 



CILIARY 



near and distant, are clear cut and definite in outline. If 
distant objects appear distinct those close by are blurred. 
Photographers understand this and when they wish to take 
a photograph of. objects at any given distance they use a 
camera in which the sensitive plate is fixed to a movable 
platform. By sliding the platform toward or away from 
the lens the image is brought to a focus on the plate. 

The eye is focused much more easily than the camera. In 
the eye the distance between the lens and the retina may be 
varied and the lens made more or less convex. The ciliary 
muscle contracts, when necessary, and pulls on the hyaloid 
membrane, bringing the retina closer to the lens, at the 

same time permitting 
the lens to swell out and 
become thicker. This 
is the condition of the 
eve when it is looking 
at objects close by. 

When it is viewing 
objects at a distance 
the muscle relaxes and 
the lens becomes flat- 
ter. The eye is focused 
for distant objects when 
we are resting and 
when we are asleep. 
When we are reading 
or looking at near-by 
objects we keep the 
ciliary muscle in a continued state of contraction, con- 
sequently it grows weary and the eye pains. When a 
person is resting or meditating we often say that his 



CORNEA 




SUSPENSORY 

LIGAMENT 



POSTERIOR 

CHAMBER 



Fig. 110. — Diagram illustrating the 
different shapes of the crystalline 
lens. 



SIGHT 263 

"mind is far away," meaning that his mind is so intent 
upon some particular thought that his eyes have relaxed 
and are focused for viewing distant objects. 

The Brain Appreciates a Single Image. — The pupils have 
learned how each eye is focused to give a distinct image, but 
they may be puzzled to know how each retina receives an 
image and yet the brain interprets the two images as one. 
That the brain does this is proved by the fact that if our 
eyes are normal and we look at a house we see one house and 
not two; if we look at a man, we see one man and not two. 

It is possible, indeed, to see two images of a single 
object. Place the forefinger of one hand in a vertical posi- 
tion two feet from the eye and the other forefinger half- 
way between and in a direct line with the other. Look at 
the nearer finger and we see but one image. Now look past 
this one at the farther finger and the nearer one appears as 
two fingers. 

This simple experiment shows that while two images are 
always formed when we use both eyes, the muscles that 
control the eyeballs so adjust them and harmonize their 
actions that the two images overlap and the brain inter- 
prets them as one. 

Illusions. — When a child first begins to use its eyes it has 
no conception of the distance of objects about it. We are 
told that very young children think that objects lying on the 
floor before them are resting against the eyeballs and they 
bring their hands close to the eyes to grasp these objects. It 
is only by experience that they come to know that the ball 
and the top and the book are at some distance from the eyes. 

By education children learn to estimate size, shape, 
form, and distance with remarkable accuracy. The ability 
to do this is extremely important in guiding them in their 



264 PHYSIOLOGY AND HYGIENE 

many movements and actions. This power to estimate 
sizes and distances under ordinary circumstances leads to 
some peculiar illusions. A hair hanging in front of the 
eye is projected into the distance as a tree or telephone pole. 
A small spider hanging from a gossamer thread in the 
direct line of vision appears on the distant horizon as a 
giant devil-fish lashing its arms in a threatening manner 
against the sky. 

Another familiar illusion is observed in connection with 
the "mote." It was stated in a previous paragraph that 
when the eyeball is packed full with the humors of the eye, 
the blood vessels are torn down and carried away. Fre- 
quently, remnants of these vessels are left in the body of 
the humors. These remnants cut off some of the rays of 
light and hence cast shadows upon the retina. As the 
eye ordinarily associates sensations with external objects, 
these shadows are projected outward where they appear 
as black spots on a white background. Inasmuch as they 
jump about in an uncertain way they are called " flitting 
flies." 

Another illusion of considerable interest may be men- 
tioned. It is a well-known fact that drunkards "see 
snakes" when in a condition of complete inebriation or 
when they are suffering from delirium tremens. This illu- 
sion has a very plausible explanation. The walls of the 
eyeball contain blood vessels as has already been explained. 
When the drunkard rolls the eyes around a portion of the 
walls is brought into the light and, being partially trans- 
parent, some of the light rays pass through; the blood 
vessels, however, being entirely opaque, shut off all light, 
and their shadows are cast on the retina as crawling, 
twisting serpents. That these snakes are real to the 



SIGHT 265 

victim is proved by his horror-stricken features and 
shrinking attitude. 

Color. — The particular rays of light that are reflected 
from a body determine its color. White light is made up of 
all colors. The house appears white because all kinds of 
rays from the sun are reflected into the eye. The barn 
looks red because the paint absorbs all the rays but the 
red which are sent to the eye. The ribbon looks blue 
because all the rays but the blue are absorbed. The blue 
rays reflected into the eye give the color to the ribbon. 

It is of interest to know that neither the house, the barn, 
nor the ribbon has any color whatever on a pitchy black 
night. Or, if we were to assume that black is a color, as 
It is not, we could say that these objects are all black on an 
extremely dark night, inasmuch as no rays of light reach 
the retina of the eye from them. The real seat of color 
lies in the retina, and the sensation of any particular 
color is determined by the kind of rays that enter the eye 
.-and impinge themselves upon this structure. 

Color Blindness. — Many people cannot appreciate some 
<of the colors. The retina lacks those properties or elements 
that are susceptible to the influence of certain light rays. 
The most common form of color blindness is the one 
in which the eye is notable to distinguish the color red. 
Many persons are color blind and do not know it. Others 
.nave discovered this defect only by the merest chance. 
Hailroad accidents have undoubtedly resulted from the 
inability of the engineer to distinguish certain colors. The 
teacher or parent can often detect this defect by bringing 
variously colored objects successively before the child's 
eyes. 

Hygiene of the Eye. — Good eyesight is one of the greatest 



266 PHYSIOLOGY AND HYGIENE 

blessings that can come to man. The power to see dis- 
tinctly and easily the many objects about them is not 
always appreciated by those who have perfect vision. It 
is only when the sight becomes dim and vision is accom- 
panied by pain and discomfort that the value of good 
eyesight is recognized. 

Young people with strong eyes sometimes think that 
nothing can affect them, that they can subject the organs 
of sight to the roughest possible usage, and it is only when 
these organs break down under the strain placed upon 
them that they realize that they have made a great mis- 
take. Children ought to be taught from childhood that 
they should guard their eyesight as they would a priceless 
jewel. A few cautions concerning the care of the eyes 
may be profitable at this time. 

Proper Sight. — In order to see well it is necessary that 
clear-cut images be formed on the retina and to get these 
definite images the eye must have plenty of light. One of the 
finest things about our modern homes and schoolhouses is 
the arrangement of the windows. It has been some time 
since the teachers learned that pupils cannot do the best 
work in poorly lighted rooms. In our well-lighted rooms 
with their large windows it is not necessary for the boys 
and girls to strain the muscles of their eyes in a vain effort 
to make out distinctly the words or objects before them. 

The matter of arranging the seats in the schoolroom is 
an important one. The windows should be placed in not 
more than two sides adjoining each other and the seats 
arranged so that the light will come from the side and 
back. In this way the pupil is not in his own light, neither 
is he compelled to face the source of light. 

Sudden flashes of strong light should be avoided for the 



SIGHT 267 

same reason that one should not read or do work of a 
similar nature in direct sunlight. In both cases the inten- 
sity of the rays is liable to paralyze the retina and produce 
partial blindness. Diffused light, such as is found in our 
modern homes, is the best for reading, sewing, writing, etc. 

Artificial Lighting. — Much of our study and reading must 
necessarily be done at night. For this reason the matter 
of lighting our rooms is of primary importance. Modern 
inventions have wonderfully improved upon the tallow 
candle and oil lamp of our fathers. To-day many of our 
homes are lighted by gas or electricity. Either of these 
is good if rightly used. 

Electricity gives a very satisfactory result if the bulb 
is not permitted to swing. However, if the current is 
weak the light is dim and red and tends to tire the eyes. 
Manufactured gas, if used with proper appliances, furnishes 
a light that is both soft and brilliant, givi»g a very 
pleasing effect to the room, at the same time producing 
a desirable light for reading. Acetylene plants have 
recently been installed in both country and city and 
furnish a gas that is admirably' suited to reading. Gaso- 
line lamps, if carefully handled, provide a" good light in 
the absence of those mentioned above. They should be 
handled, however, with extreme care. The old-fashioned 
coal-oil lamp gives a very good light when provided with 
good burners and chimneys. 

The important points to be considered in selecting a light 
are color, brilliancy, and steadiness. White light is best 
for reading and sewing. When it is not necessary for the 
eye to scrutinize small objects, colored lights may be used, 
inasmuch as they add to the charm and beauty of the room. 
A fairly bright light is desirable in most cases, especially 



268 PHYSIOLOGY AND HYGIENE 

when the eye is subjected to great and continued strain. 
In no case, however, should it be so intense as to stimulate 
the retina beyond a normal degree. Dimly lighted rooms 
are often productive of weak eyes and nervousness in 
general. 

Lights should not only be of the right color and intensity, 
but they should be steady as well. A vibrating electric 
bulb or flickering flame keeps the iris in a continual state of 
tension. Indeed, under these conditions the whole muscular 
mechanism of the eye is under a strain that can but end in 
weariness. In brief, the best artificial light is the one that 
is white or but slightly colored, brilliant without being 
harsh, and constant and steady in its action. 

Reading While in Motion. — One of the chief causes of 
defective eyesight in these days is the reading of news- 
papers on street cars and railroad trains. Business men 
rise from the breakfast table and hasten to their work, 
economizing time by perusing the daily paper while riding 
down town. Travelers buy books, magazines, and papers 
from the newsboy and spend hours in reading them while 
the cars are in motion. The jarring and rocking of the 
coaches keep the muscles of the eye constantly changing 
in tension. The balls must be frequently moved in order 
to keep the eye on the proper portion of the page. Vary- 
ing amounts of light are thrown toward the eye and, 
to regulate the quantity that enters the pupil, the iris 
is continually contracting and expanding. Moreover, the 
focus of the lens must be varied to conform to the different 
distances between the paper and the eye. This requires a 
change in the tension of the ciliary muscle fibers. The 
strain to which the eye is subjected finally exhausts the 
whole mechanism of the organ and the muscles give up in 



SIGHT 269 

despair. This overtaxing of these organs can result only 
in weakened eyes and defective vision. 

Inflammation. — The eye often becomes inflamed from 
unknown causes. Sudden changes of temperature, wind, 
smoke, dust, and gases are liable to produce inflammation. 
These causes cannot always be avoided. More frequently 
redness or inflammation is due to the pressing or rubbing of 
the lid against the ball. It is rare indeed that the eye is 
benefited by rubbing of any kind. One would much better 
endure a little pain or itching of the eye than to inflame 
it by continued rubbing. 

In all cases of inflammation the eye should be permitted 
to rest. In fact, rest is one of the best remedies for any 
temporary disorder of this organ. It gives the various 
structures a chance to recuperate and return to their nor^ 
mal condition. Continued and aggravated cases of inflam- 
mation demand the attention of a physician. 

Foreign Bodies in the Eye. — The presence of dust, ashes, 
or any other foreign bodies in the eye is easily felt. The 
end bulbs already mentioned in a preceding paragraph are so 
extremely sensitive that the smallest particle of any rough 
body produces great pain. That nature desires to eliminate 
these particles is shown by the combined efforts of the lids 
and tears. The lachrymal glands pour out an excess of 
tears and the lids violently contract in their efforts to drive 
the offending body out. Usually the lids and tears can 
eliminate these foreign bodies without any assistance, but 
often they adhere to the conjunctiva and cannot be dis- 
lodged by winking. 

When the body cannot be removed in any other way, 
it can frequently be taken out by applying the point of 
a folded handkerchief to it. Or the object may be touched 



270 



PHYSIOLOGY AND HYGIENE 




Fig. 111. 



-Pulling- back eyelid to 
remove object. 



by a swab moistened with a little oil. Sometimes it is 
necessary to roll the lid back over a pencil in order to ex- 
pose the body. In some cases a flaxseed may be floated 

under the lid. When the 
tear comes in contact 
with the seed it forms a 
sticky coat on the out- 
side, the object adheres 
to this coat and comes 
out with the seed. 

Splinters of steel are 
sometimes driven 
through the cornea into 
the humor. A powerful 
magnet placed before the eye will usually draw the frag- 
ment out. However, if possible, an oculist should be con- 
sulted in a case of this kind as well as at any other time 
when the particles resist every effort to dislodge them. 

When a body gets under the lid, the .eye should never be 
rubbed as the fragment may be driven still farther into 
the surface of the cornea. It is well to remember that if a 
body be permitted to remain in the eye for any great 
length of time it is liable to produce lasting and injurious 
effects. 

Diseases of the Eye. — Some abnormal conditions of the 
eye should be emphasized in this connection. Some of these 
conditions are inherited while others are the result of care- 
lessness or abuse of the eye. The cause may usually be 
found in the convexity of the lens, the length of the eye- 
ball, the relation of the balls to each other, or the condition 
of the humors or coverings. A brief description will be 
given of some of the most important diseases. 



SIGHT 



271 




Fig. 112. — Diagram short sight. 



Short Sight. — Often the eyeball is so long that the lens 
brings the rays of light to a focus before they reach the 
retina. Or the 
lens may be so 
convex that the 
effect is the same; 
that is, the image 
is formed in front 
of the retina. In 
either case, rays 
of light coming from objects at a distance produce a 
blurred image. A person who is thus affected holds the 
object close to the eye; in this way the image may be 
formed far enough back to fall upon the retina. 

A condition of this kind should not long be tolerated. 
The remedy is concave glasses. It is well known that 
lenses that are thick at the edges and thin at the mid- 
dle have the power to scatter rays of light. Since the 
tendency in short sight is to bring the rays to a focus too 
soon, concave lenses placed in front of the eyes will scatter 
the rays and cause the image to fall on the retina; a clear- 
cut image is the result. 

Long Sight. — The conditions described in the preced- 
ing paragraph may be reversed. The ball may be too 

short or the lens 
too flat, or both 
of these conditions 
may exist at the 
same time. In 
either case the 
rays of light are 
not brought to a 




Fig. 113. — Diagram long sight. 



272 PHYSIOLOGY AND HYGIENE 

focus soon enough, consequently, if an image were formed 
at all it would fall back of the retina. The fact is, no 
image is formed, or if it is formed, it is blurred and indefi- 
nite in outline. 

Since rays of light coming from a distance are brought to 
a focus nearer the lens than those emanating from objects 
close by, one who is suffering from this condition is inclined 
to hold the object viewed at arm's length that he may see 
better. At the very best, however, the eye is strained and 
only an indistinct image is produced. The remedy is to use 
convex spectacles. These offset the flatness of the crystal- 
line lens and the image is thrown upon the retina. It will 
be observed that persons afflicted with this disease can 
see objects at a distance quite readily. This condition 
is known as far sight. 

Old Sight. — As the heading implies, this is a condition of 
old age. We probably have already learned that as the 
body grows older the various tissues of which it is composed 
grow harder and the muscles become less elastic and con- 
sequently less able to perform their functions. What is 
true of the body in general is true of the eye in particular. 
As old age approaches the humors and walls become stiff 
and hard, and, as the muscles are unable to perform their 
duties as they once did, the eye can no longer focus the lens 
properly. As the natural focus of the eye is for distant 
objects, the accommodation for old age is such that objects 
far away may be seen most distinctly. It is to be observed, 
however, that the eye can be focused easily for objects at 
only one certain distance. To make it possible for objects at 
other distances to be seen distinctly, it is necessary for the 
person to use spectacles especially ground. Usually at least 
two pairs of glasses or lenses are required for old sight. 



SIGHT 



273 



Astigmatism. — Not all eyes are able to see with equal 
distinctness two sets of lines perpendicular to each other. 
Concentric circles lying very close to each other appear 
to some eyes blurred or wavering at certain points on 
their circumference. This is due to the unequal curva- 
ture of the cornea or lens. If a portion of the surface 
of either of these structures is flattened, the rays pass- 
ing through this portion are brought to a focus back 
of the focus of the other rays. Since the retina can- 
not be brought to . a focus of all the rays, the image 
is necessarily blurred along certain axes of the eyes. 
This condition is known as astigmatism. Lenses es- 
pecially ground to offset the flattening of the eye should 
be used. 

Cataract. — Frequently a cloudiness forms in the humors, 
the lens, or the cor- 
nea of the eyes. 
If this cloudiness 
becomes extended 
enough, it ren- 
ders the part af- 
fected opaque. 
Since no light can 
pass the opaque 
portion, no image 
is formed direct- 
ly behind it. In- 
deed, the cloudi- 
ness may spread 
entirely across the eye, preventing the formation of any 
image whatever. 

This disease, known as cataract, is one of the most 




Fig-. 114. — Beginning- of a cataract. 



274 PHYSIOLOGY AND HYGIENE 

serious conditions of the eyes. In many cases there is 
no remedy. If the opacity is due to a growth over the 
front of the cornea, the condition may be relieved by 
removing the clouded matter from the surface of the 
cornea. It has been stated on good authority that the 
diseased crystalline lens has been removed by skillfully 
cutting into the side of the eye, and inserting a specially 
ground glass lens to take its place. It is evident that 
the glass lens would not permit of any changes in its 
shape, consequently its focus would always be at the 
same point. 

Cross-Eyes. — Occasionally the muscles of the eyeballs 
are not of the same strength on both sides; as a result, one 
pulls harder than the other, the ball turns inward or out- 
ward, and two images are seen. When one of the balls is 
rotated inward, its line of vision crosses that of the other. 
This condition gives rise to cross-eyes. When the outer 
muscle is stronger than the inner, the eye is rotated 
outward and wall-eyes are the result. When the eye is 
pulled aside but little, the condition is known as the 
squint. 

The remedy in all these cases is to have a reliable ocu- 
list cut some of the fibers of the stronger muscle. This will 
permit the eye to return to its natural position, when but 
one image is seen again. Parents should look after their 
children's eyes early if they are troubled in this way. The 
effort required to secure clear vision leads to pain in the 
eyes and headache. Moreover, this condition leads to a 
timidity and backwardness that will affect the whole after 
life of the child. 

Alcohol and the Senses. — Alcohol frequently causes 
defective eyesight by affecting both the optic nerve and 



SIGHT 275 

blood vessels. By deadening the olfactory cells and taste 
bulbs alcohol destroys the acuteness of the senses of smell 
and taste. The end organs of hearing are often rendered 
less sensitive by the action of this narcotic. 



CHAPTER XXX 

STIMULANTS 

Drugs. — Reference has been made from time to time to 
the use of various substances other than food, and the 
effect of the same on the mind and body. The term drug 
is commonly applied to these substances, although the word 
has a very broad meaning, including various chemicals and 
preparations used as medicines. It is not necessary to dis- 
cuss the drugs that are used only for medical purposes, but 
every young man and young woman should know something 
of the nature of those that are used improperly, are ex- 
tremely injurious, and lead frequently to the formation of 
bad habits. The latter include stimulants, narcotics, and 
poisons. 

Stimulants. — These are drugs or preparations that tend 
to excite organs or parts to increased activity. It is not to 
be supposed that stimulants are always injurious. Even 
a good horse may require the application of the whip to get 
it to pull an exceptionally heavy load over a difficult place 
in the road. But no humane driver would flay the animal 
with the whip all day long regardless of consequences. 
Such a treatment would soon use up the energy of the 
horse, and its value as a beast of burden would be perma- 
nently impaired. 

So it is with the human being. There are times when the 
organs grow weak and the energies begin to flag. At such 
times the use of a stimulant may be necessary to urge the 

276 



STIMULANTS 277 

parts affected to greater activity in order that a crisis may 
be passed. But it should be remembered that physical or 
mental depression is the result, and the body must have a 
period of rest so that it may regain strength. Some of our 
common stimulants are alcohol, ammonia, tea, coffee, and 
cocoa. 

Alcohol. — We have often noticed the peculiar biting 
taste of fruit that has become slightly fermented. Sweet 
cider, after standing for some time, develops a sharp, 
penetrating taste that suggests the presence of some new 
substance; this taste is due to the presence of the well- 
known stimulant, alcohol. 

How Alcohol is Made. — Fruits and grains and in fact 
many vegetables contain an insoluble substance called 
starch together with a certain amount of sugar. Alcohol 
cannot be made directly from starch, so this substance is 
changed into sugar. The sugar is then acted upon by. 
numerous bacteria which exist in the air and is broken up 
into alcohol and carbon dioxide. Water boils at a much 
higher temperature than alcohol, hence the latter may be 
removed by keeping the mixture of the two at a tem- 
perature between the two boiling points. The process 
of separating two liquids in this way is called distillation. 
The alcohol is passed through a tube surrounded by cold 
water and being condensed is collected in a proper vessel. 

Properties and Uses of Alcohol. — While this stimulant is 
exceedingly harmful when used improperly, it is one of the 
most useful of substances in the sciences and arts. This 
use depends upon its peculiar properties. 

As has been suggested, it has a sharp, burning taste and, 
besides, has a characteristic pleasant odor. Since it boils 
at a low temperature it is very volatile. It freezes at a very 



278 PHYSIOLOGY AND HYGIENE 

much lower temperature than water and is sometimes used 
in thermometers. It has a strong affinity for water. 

If an organic body such as a piece of lean meat be placed 
in it for some time it extracts the water, leaving the meat 
hard and dry as though it had been cooked. On account of 
this property it is used as an antiseptic, animal specimens 
being preserved in it for an indefinite time. 

It is used to hold in solution certain resins and oils that 
do not dissolve readily in water or other solvents. It is one 
of the principal ingredients in many essences, extracts, 
perfumes, and medicines. It burns quietly with a clear 
colorless flame, producing intense heat. For this reason it 
is valuable in laboratories where gas is not obtainable. 

Denatured Alcohol. — The use of alcohol has been so 
abused that several states have wisely passed stringent 
laws prohibiting its manufacture, sale, and use as a bev- 
erage. But in the past the restrictions placed on its sale 
have been so severe that they have practically prohib- 
ited its use for scientific purposes. To make it possible 
for the states to prevent its sale as a beverage and at the 
same time permit its use in the sciences and arts, Congress 
proposes to make it unfit for drinking by rendering it 
poisonous. 

Wood alcohol is a poison, yet it has many of the properties 
that make common alcohol valuable. By combining the 
two a mixture is secured which is extremely poisonous, but 
which has the qualities so desirable as a commercial product. 
This and other methods have been proposed for poisoning 
alcohol. A product of this kind is called denatured alcohol. 

A coloring matter is added so that the true nature of the 
alcohol may be known. As alcohol can be made from 
decayed fruits, melons, and other refuse matter, it can be 



STIMULANTS 279 

produced cheaply and used for both heating and lighting 
purposes. 

Alcoholic Beverages. — While alcohol is one of the most 
valuable of substances when used in the proper place and 
in the right way, its abuse has caused more misery and 
sorrow than any other single agency. Inasmuch as the 
evils of alcohol grow out of its use in the form of alcoholic 
beverages it is well that young people be taught some- 
thing of the manufacture of these drinks and the amount 
of alcohol contained in them. Alcoholic beverages may 
be classed under three divisions : fermented liquors, malt 
liquors, and distilled liquors or spirits 

Fermented Liquors. — As has already been stated, these 
are produced from the sweet juices of fruits and vegetables 
by the action of certain bacteria that exist in the air. The 
germs attack the sugar and break it up into alcohol and 
carbon dioxide. Among fermented liquors are cider, wines, 
and root beers. Cider contains from two to five per cent, 
and wine from seven to twenty per cent, of alcohol. 

Malt Liquors. — While fermented liquors are usually 
made from fruits, malt liquors are prepared largely from 
grains. The grain is first germinated by warmth and 
moisture. This step changes the starch into sugar. At the 
proper time the germinating process is stopped by roasting 
the grain to kill the germ. It is then mashed and trans- 
ferred to large vats where it is mixed with warm water. 
Extracts are added to give flavor to the product and yeast 
introduced to produce fermentation. The amount of alco- 
hol is determined by the peculiar treatment to which it is 
subjected. The common malt liquors are beer, porter, 
ale, and stout. These contain alcohol varying in amount 
from four to fifteen per cent. 



280 PHYSIOLOGY AND HYGIENE 

Distilled Liquors or Spirits. — Spirits are drinks that are 
made by distilling fermented liquors. The oftener they are 
distilled the greater per cent, of alcohol they contain. 
Brandies are distilled from wines and contain from fifty to 
sixtj T per cent, of alcohol. Peach brandy is prepared by 
distilling wines made from the peach. Rum is distilled 
from molasses, and whisky from fermented grain and 
potatoes. The former contains from fifty to sixty per cent, 
and the latter from forty to fifty per cent, of alcohol. 

The Evils of Alcoholic Drinks. — If a foreign army were 
to land on our shores and proceed to march through our 
most densely populated areas, laying waste our farms, burn- 
ing our houses, and massacring our people, the men of the 
nation would rush to the call of arms and drive the enemy 
into the sea. Let the word go out that yellow fever or the 
bubonic plague has gained a foothold in our large cities and 
at once the intelligence of modern medical science is called 
into action in order to prevent an epidemic of disease and 
death. 

But we are confronted with an evil greater than either 
of those mentioned. The habit of strong drink has so 
grown upon men that thousands are annually hurried into 
an untimely grave and thousands of others are oppressed 
by conditions even worse than death. These conditions, 
supplemented by the wise instruction of our young people 
concerning the effects of intoxicating liquors, have in re- 
cent years produced a reaction which will undoubtedly 
lead to a correction of one of the greatest evils of mod- 
ern times. That the boys and girls may know in a defi- 
nite way some thing of the injurious effects of alcoholic 
beverages, a few paragraphs of explanation are in place 
at this time. 



STIMULANTS 281 

Alcohol as a Stimulant. — When liquors containing 
alcohol are taken into the system the alcohol does, for a 
short time, act as a stimulant. But this action is brief. 
The various organs are driven to overexertion and then 
begin almost immediately to grow weak and exhausted. 
The final result is a complete depression of the whole body. 

Other Effects of Alcohol. — As soon as the alcohol reaches 
the organs they immediately respond as indicated above. 
The heart's action increases, the capillaries on the surface 
of the body enlarge and the blood rushes to fill them up. 
A period of excitement follows during which the drinker 
becomes communicative. Gradually he grows drowsy and 
perhaps falls asleep. The next day the drowsiness passes 
away and the recovery from the depression follows. 

Continued Use of Alcoholic Beverages. — The small 
amounts of dilute alcohol taken by the moderate drinker 
soon fail to produce the agreeable feeling and pleasurable 
excitement that followed the first indulgence. To secure 
the desired effect larger doses are necessary. These cause 
an increased surging of the blood to the surface of the body 
and the delicate walls of the stomach and intestines. The 
brain is affected by the alcohol and the individual becomes 
more talkative. His nerves feel the influence of the strange 
substance, the drinker trembles in his movements and 
walks with an unsteady gait. As the alcoholic effects begin 
to pass away he falls into a deep sleep from which he is 
aroused with difficulty. When consciousness is restored 
a longer time is required to permit of a return to complete 
strength and vigor. 

Intoxication. — The taste for alcohol begets a stronger 
taste for itself. Larger quantities yet must be taken to 
bring about the original feelings of pleasure and excitement. 



282 PHYSIOLOGY AND HYGIENE 

The blood vessels now become permanently enlarged and 
the flushed face easily shows the distended veins and 
arteries. The narcotic principle of the beverages deadens 
the nerves and brain tissue and the victim staggers along 
the street or falls into the gutter or the alley, dead drunk. 

Final Stages of Intoxication. — As time goes by and the 
habit of drinking grows on the man, he forgets everything 
else in his cravings for his whisky or brandy. With all 
feelings of self-respect gone and lacking in power to control 
his actions and restrain his appetite he plunges recklessly 
into the indulgence that has broken his will power and 
destroyed his manhood. With bloodshot eyes and hag- 
gard face, he reels wildly down the street only to drop 
finally into the gutter, in a state of absolute unconscious- 
ness, an object of shame to his friends and ridicule on the 
part of thoughtless bystanders. 

Delirium Tremens. — But often there is a condition far 
worse than the one mentioned above. The vicious in- 
fluences of alcohol begin to tell on the mind of the drinker 
and he loses all control over his thinking powers. The 
imagination is abnormally stimulated and the mind con- 
jures up strange, unnatural pictures. Fantastic forms and 
figures flit before his vision and he is the subject of wild 
hallucinations. These figures finally assume the form of 
snakes and goblins, and demons which threaten to destroy 
him. In his wild despair he struggles frantically with these 
imaginary enemies and strikes helplessly about him. 
Even those who are near and dear seem to surround him and 
torment him. As his energy is gradually exhausted he sinks 
into a semicomatose condition from which he starts sud- 
denly with shrieks of terror. Finally, nature asserts itself 
and he drops into a state of complete unconsciousness. 



STIMULANTS 283 

This condition of mental torment is called delirium 
tremens. A more miserable and pitiable state cannot be 
imagined. It is needless to say that this is the final stage in 
alcoholism. With the organs of digestion honeycombed 
with cancerous growths, with the muscle fibers of the heart 
decomposed and replaced by fatty tissue, with the nerves 
of the blood vessels paralyzed, with the devitalized blood 
streaming to the surface of the body liberating an abnormal 
quantity of heat, with the whole nervous system inebriated, 
the matter of death is only a question of time. 

Moral Effects of Alcohol. — We have already learned 
that the use of alcohol begets a craving for itself. It 
weakens the will power, and impairs the different processes 
of thought. Inasmuch as the nerve cells are gradually 
destroyed, confusion of memory necessarily follows. As a 
result of the breaking down of the whole intellectual 
structure, the victim of strong drink grows suspicious and 
treacherous. His knowledge of his own weakness leads to a 
loss of self-respect. His cravings for beer or whisky often 
develop deceit and dishonesty. When the desire for in- 
toxicants cannot be satisfied in any other way, the victim 
not infrequently resorts to lying and theft. Compromising 
himself more and more there comes a time when under the 
influence of alcohol he fires the shot that takes the life of a 
fellow-being. 

Even if his appetite does not lead him to these extremes, 
he gradually loses those finer qualities that are charac- 
teristic of the true gentleman. He is cross and ugly in the 
home and disagreeable to those about him. Instead of 
being a real helper and true supporter of his wife and an 
inspiration to his children, he brings to the home only 
misery, gloom, and disappointment. The home of the 



284 PHYSIOLOGY AND HYGIENE 

drunkard is a continual scene of wretchedness, anguish, 
and despair. Often the children go without clothing and 
proper food. Even when they are supplied with the neces- 
sary books for school use, the taunts and gibes of their 
thoughtless playmates make attendance almost unbearable. 
The sad thing about it is the fact that those who suffer the 
most are the innocent mothers, wives, and children. 

Alcohol Not a Food. — Some people excuse the use of 
intoxicants on the ground that alcohol is a food. Much has 
been offered by scientists and others, both for and against 
this view, so that it is difficult to get at the real facts of the 
matter. Those who believe that it is a food offer in sup- 
port of their belief the statement that alcohol is oxidized in 
the body. While this statement has not been proved to 
the satisfaction of everybody, it is probable that small 
quantities are oxidized. 

But oxidation of a substance in limited amounts does 
not make of it a food in the true sense of the word. Foods 
are those substances which, taken into the body, build up 
its tissues or give it heat and energy. Even if it is true that 
alcohol oxidizes in limited amounts, the resulting heat or 
energy is small compared with the quantity dissipated from 
the body due to the presence of the alcohol. Admitting 
that alcohol does oxidize, and admitting that for this reason 
it may technically be called a food, we are forced to the 
conclusion that practically it is not a food at all, inasmuch 
as the body would be better off without it from the view- 
point of assimilation. 

This position is further emphasized by the fact that as 
soon as alcohol is taken into the system, nature seeks every 
possible means of getting rid of it, which would not be true 
if it were a real food. Within a short time after alcohol gets 



STIMULANTS 285 

into the blood its presence may be detected in the breath 
by its odor. The body seeks to throw it off through the 
lungs. It is evident, from what has just been said, that 
those who would justify the use of alcohol on the ground 
that it belongs to the class of foods, must advance some 
better proofs to sustain their position than those that have 
been given heretofore. 

Conclusions Reached by the Business World. — The day 
is past when the man who takes a stand against the use of 
alcoholic beverages is considered an irresponsible crank. 
Our complex industrial system has done much toward 
advancing the cause of temperance. The great loss 
of life and destruction of property resulting from the 
employment of men addicted to the, use of alcoholic 
beverages has done what temperance agitation alone could 
not do. 

Capital is no longer willing to intrust the care of its 
property to the hands of the heavy drinker. The public in 
general is loath to believe that the brain steeped in alcohol 
can guide the speeding passenger train safely over bridges, 
through tunnels, and across mountain gorges. Wise busi- 
ness men have come to know that it takes a clear head and 
steady nerve to conduct successfully the affairs of a modern 
industrial concern. Most railway and street-car companies 
now demand that their employees refrain from the use 
of intoxicating liquors in any form while on duty. Indeed, 
some of them have taken an advance step and require 
total abstinence on the part of every person under their 
supervision. It is only a question, of time until all of our 
large business concerns and organizations will ask that 
every man. in their employ become total abstainers or 
else step down and out. Will the boys of to-day form 



286 PHYSIOLOGY AND HYGIENE 

such habits and build such characters as will prepare them 
for the demands of the future ? 

Alcohol as a Narcotic. — Alcohol is not only a stimulant 
but a narcotic as well. It extracts water from the nervous 
tissue, leaving it hard and dry. We have shown that the 
continued use of alcoholic beverages produces drowsiness, 
sleep, and complete unconsciousness. The paralysis of the 
nerves, common to the drinker, is due to the narcotic effect 
of alcohol. Indeed, the stimulating effects of alcohol are 
not so serious as its narcotic effects. 

Alcohol as a Poison. — Inasmuch as alcohol tends to 
destroy the health of practically every organ of the body, 
it may be classed as a true poison. The fact that strong 
doses of alcohol produce death only emphasizes the poison- 
ous nature of the substance. 

Ammonia. — This is a sharp, penetrating, pungent gas 
that has a peculiarly suffocating effect on the lungs. It is 
very soluble in water and in this dissolved form is usually 
sold at the drug and grocery stores as ammonia or ammonia 
water. Under the name of spirits of hartshorn it is brought 
into service as smelling salts, the volatile gas acting as a 
stimulant to the mucous membrane of the nose. It is used 
by the housewife to clean glassware and other kitchen 
utensils. In addition it is a valuable reagent in the 
laboratory. Occasionally it is mistaken for medicine. It 
can usually be detected by its odor, and by the irritation 
of the membranes of the eyes and nose. It produces a 
violent burning or caustic effect when swallowed. Its 
antidote in the case of suffocation is the vapor of muriatic 
acid. In the case of swallowing, either very dilute muri- 
atic acid or vinegar should be administered. 

Tea. — This drink is an infusion of the steeped leaves of 



STIMULANTS 287 

the tea plant. It contains certain volatile oils and the alka- 
loid thein. Tea is used as a beverage by all civilized races. 
The dried leaves are imported largely from Japan and 
China, although the plant is now cultivated in many parts 
of the world. Besides oil and thein, tea contains tannin. 
Tea is a mild stimulant and is a valuable drink for adults. 
Its use should be avoided, however, by young people and 
older persons when it produces nervousness and sleepless- 
ness, as it frequently does. 

Coffee. — Like tea, coffee must be classified as a mild 
stimulant. It is an infusion of the roasted and ground seed 
of the coffee tree and contains the alkaloid caff e in. Be- 
sides being a stimulant it is a real food, furnishing material 
for the nourishment of the tissues. Its value in this respect, 
however, is not great. It stimulates the nervous system, 
thus tending to increase the action of the heart and 
frequency of the pulse. It undoubtedly lessens fatigue in 
the case of old people and promotes cheerfulness and buoy- 
ancy. Children do not need coffee and for that reason should 
not use it. Experience seems to prove that alkaloids in 
coffee tend to prevent the normal development of tissues. 
Often in older people coffee causes nervousness and sleep- 
lessness. In all cases of this kind its use should be discarded. 

Cocoa. — This is a drink prepared from the ground seed 
of the cocoa tree and contains the alkaloid theobromine. 
Cocoa is used as a beverage and contains a much greater per 
cent, of food elements than either tea or coffee. Like those 
beverages cocoa is a stimulant, but it is more nourishing and 
does not produce the unpleasant effects caused by their use. 

Other Stimulants. — Absinthe, cocaine, hasheesh, opium, 
and some other drugs are stimulants, but will be discussed 
under the subject of narcotics. 



CHAPTER XXXI 

NARCOTICS 

A Narcotic Defined. — A narcotic is a substance which 
deadens pain, blunts the senses, induces sleep, and if taken 
in sufficient quantities produces convulsions, complete in- 
sensibility, and finally death. A narcotic whose chief effect 
is to induce sleep is called a hypnotic, while one administered 
for the purpose of preventing or allaying pain is known 
as an anaesthetic. 

There are a few narcotics with which all should be familiar. 
Not only should the general symptoms of these be under- 
stood, but a knowledge of the proper antidotes or remedies 
is essential. It is well to remember that many of the 
narcotics are also poisonous. Only a brief discussion will 
be given of the following narcotics. For a wider treatment 
of these drugs a more advanced text should be consulted. 

Absinthe. — This is a common drink among the French 
people and lately has been introduced into the United 
States. It is made by pounding up the leaves and flowers of 
wormwood with angelica, sweet flag, or other aromatic 
roots and mixing with alcohol. The product is then dis- 
tilled. It is a greenish, bitter, aromatic liquor and, as a 
medicine, is used to check fevers and as a tonic. It pro- 
duces all of the symptoms of alcohol, producing intoxica- 
tion, convulsions, hallucinations, delirium tremens, and, in 
extreme cases, insanity. As in case of intoxication by 
alcohol dashes of cold water should be thrown on the 

288 



NARCOTICS 



289 



victim, spirits of ammonia administered, and the legs and 
feet vigorously slapped with the hand. 

Aconite. — This is a narcotic poison secured from certain 
plants. It is used as a medicine to suppress fevers and 
relieve neuralgia. It produces numbness or tingling sensa- 
tions in the throat and skin. Emetics, or those substances 
that produce vomiting, should be given to get the aconite 
out of the stomach. 

Artificial respiration should be carried on. This may be 
accomplished by placing the individual on his back. The 
arms should then be drawn up and back 
on each side of the head. This enlarges 
the chest cavity and permits the air to 
pass into the lungs. By bringing the 
arms forward and down to the sides of 
the body and pressing on the breast bone 
the air is again driven out. By repeat- 
ing this process about eighteen times a 
minute, natural respiration may finally be 
restored. 

Belladonna. — We are all familiar with 
the large plant that grows along the side 
of the road and in waste places called the 
nightshade. Its flowers are much like the 
morning glory but considerably larger. From this plant is 
extracted a drug of peculiar narcotic properties. It is used 
to relieve pain and check spasms. It has the property , 
however, of dilating the pupil of the eye. The oculist takes 
advantage of this in examining the interior of the eye. On 
account of the fact that it was formerly used by the Spanish 
ladies to enlarge the pupil of the eye and give it beauty, this 
drug was called belladonna, a word meaning beautiful lady. 




Tig. 115. — Night- 
shade plant. 



290 



PHYSIOLOGY AND HYGIENE 



It may be known by the above-named property and by the 
fact that it produces stupor. The antidotes are dashes of 
cold water in the face, paregoric or laudanum. 

Chloral. — This is a white crystalline drug that is used as 
a hypnotic, inducing a calm sleep. Overdoses paralyze the 
nerve centers and often produce death. In case of poison- 
ing by chloral, cold water should be thrown on the person, 
stimulants administered, and artificial respiration applied. 
Chloroform. — Chloroform is a volatile, colorless liquid 
of an agreeable taste and smell. Its vapor is inhaled as an 
anaesthetic. It produces intoxication, muscular contrac- 
tion, dreaming, and insensibility. Antidotes are the same 
as for chloral. 

Cocaine. — This is a narcotic obtained from the leaves of 
the cocoa tree of South America. Its properties are due 
to the presence of a bitter alkaloid. It 
is used as a local anaesthetic. The phy- 
sician administers it by means of a hypo- 
dermic needle. The cocaine is in this 
way forced under the skin, where it 
deadens the parts immediately about the 
point of insertion. However, its effects 
are felt over the entire body. 

Like most of the narcotics, cocaine de- 
velops a craving for itself. After a per- 
son uses it for some time he cannot get 
along without it. Regularly every day at 
Fig. 116.— Branch the same hour the drug must be injected 
of a cocoa tree. or the sufferer becomes crazed. The 

longer the narcotic is used the stronger the habit grows 
until the victim is reduced to a condition of bondage more 
abject than that of physical slavery. 




NARCOTICS 291 

The craving for the drug is so urgent that the whole 
character is undermined and the victim resorts to decep- 
tion, trickery, or theft in order to secure even temporary 
relief from his torture. Unless the doses are administered 
regularly the unfortunate individual often raves like a 
madman; his actions furnish sufficient reason for the use of 
the expression " cocaine fiend." 

An instance that came under the writer's observation 
might be cited. A highly educated man, who was a 
splendid painter, formed the cocaine habit. Formerly a 
gentleman, kind and considerate of his family, honest and 
industrious, he occupied a position of trust and influence 
in the community. As this terrible habit grew on him, he 
gradually disposed of his home furniture to purchase the 
narcotic. Reduced to poverty, he finally resorted to lying 
to secure the drug. After taking some of the cocaine he 
would return to work only to be harassed once more by the 
tireless craving for more. Losing the confidence of his 
employers and the respect of his fellow-men, with health 
shattered and will power gone, friendless and homeless, the 
wretched creature suddenly disappeared, probably going 
the way of hundreds of others who submit to the illusive 
effects of this drug. 

Cocaine is not only a narcotic but a stimulant as well. In 
case one is called upon to treat a person who is under the 
narcotic influence of cocaine, he should first administer 
a stimulant such as ammonia, then follow with dashes 
of cold water, slapping the body with wet towels, and 
finally in extreme cases he should produce artificial respi- 
ration. 

Ether. — Ether is a light, colorless, inflammable liquid 
with a very refreshing odor. It is used as a solvent for 



292 



PHYSIOLOGY AND HYGIENE 



certain drugs, such as resins and alkaloids. Its effects and 
antidotes are very much like those of chloroform. 

Hasheesh. — This is a preparation of the dried leaves 
of Indian hemp. It is smoked much like tobacco and is 
sometimes used as a drink. Formerly 
warriors and murderers took hasheesh to 
stimulate them to the performance of ex- 
treme deeds or actions. On account of 
this fact they are called " hasheesh eat- 
ers/' from which expression developed 
our term assassin. Hasheesh is a stim- 
ulant as well as a narcotic, producing 
intoxication and hallucination. Cases of 
hasheesh poisoning should be treated as 
was suggested for cases of cocaine poi- 




Fig. 117 

hemp 



Indian 



Strychnine. — Strychnine is a white, 
bitter powder secured from the seed of 
the nux-vomica tree of India. It is administered as a 
stimulant in cases of great exhaustion or paralysis. It 
produces convulsions or spasms and its presence in the 
system may be surmised on account of these effects. Inhal- 
ing chloroform or ether is a remedy for strychnine poi- 
soning. 

Opium. — This, the most seductive of all narcotics, is 
obtained from the dried juice of the poppy plant. It con- 
tains a substance called morphia, which is the essential 
principle of laudanum, paregoric, morphine, soothing sirups, 
etc. It is used as a medicine to allay pain, relax spasms, 
and induce sleep. Its symptoms are about as follows : When 
first taken it soothes the nervous system, increases the 
temperature of the skin, and greatly stimulates the mental 



NARCOTICS 293 

activities. As the opiate continues to act, intoxication sets 
in, followed by delirium, after which joyous dreams and 
pleasing fancies flit through the mind in quick succession. 
Finally, the brain is completely overcome by the narcotic 
and the individual drops off into a deep, unrefreshing sleep. 
When the force of the drug has exhausted itself, the victim 
awakens out of the stupor with a headache and nervousness, 
from which he slowly recovers. 

What was said of cocaine can be emphasized here with 
reference to opium. Opium is one of the most delusive, 
insidious narcotics misused by man. Opium eaters and 
smokers form a habit that is relentless in its exactions. 
The opium dens, of our large cities stand for all that is 
low and vile and degrading. Pictures of these miserable 
resorts show reclining figures in all stages of narcotism. 
Pale, emaciated, hollow-cheeked creatures draw patiently 
away at the nerve-destroying opium pipes, living a dreamy, 
happy existence. They drag their shrunken bodies out on 
the streets, only to return to the seductive charms of the 
pipes. Business is neglected, friends forsaken, and all that 
is pure and good forgotten in the vain effort to satisfy the 
cravings for the narcotic. 

Well, we say, there is no danger of our forming such a 
habit. But let us remember that many of our medicines 
contain opium, and the continued use of these is liable to 
fasten the craving for the same upon us before we are aware 
of it. The use of morphine, paregoric, and the so-called 
soothing sirups, is dangerous unless under the direction of a 
wise and intelligent physician. The treatment for opium 
poisoning is the same as that for cocaine and hasheesh. 

Tobacco. — Tobacco is a plant that contains a narcotic 
principle called nicotine. This principle took its name from 



294 



PHYSIOLOGY AND HYGIENE 




Jean Nicot, who once sent some tobacco to the Queen of 
France. Tobacco was originally used by the Indians, but 
has in recent times been introduced into every civilized 
country of the globe until it is more widely used than any 
other narcotic. It is smoked, chewed, and 
taken as snuff. The general effects of 
tobacco are to induce physical and mental 
quiet, produce confusion of mind, and 
loss of memory with dizziness and vomit- 
ing. The use of tobacco leads to two 
serious diseases — " smoker's cancer" and 
" tobacco heart" — conditions that have 
already been discussed. As the effects 
of tobacco on different parts of the body 
have been given in other parts of the 
book, they need not be further discussed 
here. 

Cigarettes. — The most pernicious form 
of tobacco is the cigarette. Made in imitation of the cigar, 
it contains all of the injurious elements of that article, as 
well as some that are not found in the cigar. In order to 
make the cigarette cheap it is adulterated with various 
substances, many of them extremely poisonous in their 
natures. In addition, other injurious ingredients are added 
to give flavor to the cigarettes and neutralize the unpleas- 
ant effects of the adulterations. The resulting mixture is 
so harmful to the system that the evil effects are quite no- 
ticeable soon after the boy begins to smoke. The skin be- 
comes sallow, while the boy grows restless and nervous. 

The worst feature of cigarette smoking is that the liber- 
ated poisons are taken in by the breath, get into the blood, 
destroy the cells, and prevent their repair and development. 



Tig. 118.— Poppy 

plant. 



NARCOTICS 



295 



As a result the organs do not mature and the body becomes 
shrunken and dwarfed. The brain cannot develop properly, 
consequently the youth is unable to apply himself success- 
fully to his studies. Finally, he becomes discouraged and 
drops out of school, diseased in body and mind. Once on 
the street he too often begins that downward course that 
ends in disaster, physically, morally, and intellectually. 
How suggestive is the term " coffin nails" when applied to 
cigarettes. Would that every schoolboy could appreciate 
the fact that every cigarette smoked may some day in the 
near future prove to be a nail driven into his own coffin. 

A Bad Habit. — It is right that young people should 
know from the start that the use of tobacco is unnatural. 
Is it not true that young men become 
very sick when they first use tobacco ? 
The vomiting that results from the first 
introduction of tobacco into the system is 
nature's effort to get rid of the poison. It 
is only after long-continued use of the 
narcotic that the system gives up its un- 
successful struggle. 

The effects of nicotine on the various 
organs have been mentioned in other 
chapters, and it need only be observed 
here that the use of tobacco tends to 
blunt those finer sensibilities of the mind 
that make men kind, unselfish, and con- 
siderate of the rights and feelings of others. Our friends 
who have formed the tobacco habit sometimes tell us that 
they buy the tobacco, smoke or chew it themselves, and 
if there are any evil results they alone suffer, and, conse- 
quently, the matter is of interest to them alone. 




Fig. 119— Tobacco 
plant. 



296 PHYSIOLOGY AND HYGIENE 

But is this true ? Does their habit affect the rights of 
others? A lady was dropping some letters into the mail 
box at the post office, when one of them slipped from her 
hand to the floor. Upon picking it up she found that it was 
soaked with vile-smelling tobacco juice. Imagine the lady's 
feeling of disgust. Did the man who expectorated on the 
floor interfere with the rights of others ? 

Ordinances are passed in our cities prohibiting the dis- 
charge of waste matter from closets and cesspools into the 
alleys and streets. Manufacturing concerns are no longer 
permitted to turn loose injurious and offensive gases, inas- 
much as they affect the health and comfort of the people 
at large. Yet the user of tobacco feels privileged to befoul 
the floor with tobacco juice and fill the air of our public 
buildings with ill-smelling tobacco smoke. Men lacking 
in the nicer feelings of refinement and courtesy force their 
way into coaches and waiting rooms set apart for ladies and 
charge the whole atmosphere with the offensive fumes of the 
narcotics. 

Not all men, of course, are guilty of this discourtesy, but 
the fact that such a large number, thoughtlessly or in- 
tentionally, make themselves obnoxious in this way justifies 
a condemnation of the tobacco habit in no uncertain terms. 
It is worthy of note that but few of them desire that their 
sons should form the habit. How often have we heard an 
old man say that he wished that he had never become ad- 
dicted to the use of tobacco ; but how many of us have heard 
anyone say after he had reached maturity that he was sorry 
that he had not learned to smoke or chew? The truth is, 
most boys use their first tobacco because they think it 
makes a man of them or else they fear the ridicule of their 
companions. But the manly boy is the one who is strong 






NARCOTICS 297 

enough to resist temptation and show his friends that even 
ridicule cannot make him do what he believes to be wrong. 

Tobacco and Physical Requirements. — Much has been 
said concerning the effects of tobacco on length of life. 
Tobacco users gleefully refer to newspaper accounts of men 
who have used tobacco and alcohol all their lives and have 
yet reached the age of one hundred years. In many cases 
these are exaggerations; and where they are not they prove 
the exception. It cannot be successfully disputed that 
tobacco shortens life. 

Not only that, but ; as has been suggested, it prevents the 
full development of the bodily organs. Statistics show that 
more young men fail to pass the requirements for entrance 
to the army and navy on account of the use of tobacco than 
for any other cause. Almost without exception the boys 
who abstain from smoking and chewing make better 
athletes than those who do not. Trainers recognize this 
fact and prohibit the use of narcotics during the period 
of practice and competition. Unprejudiced investigators, 
whether they use tobacco or not, agree that, all other things 
being equal, the physical make-up of the abstainer is more 
perfect and will stand greater strain and exertion than will 
that of the user. If this is true, ought it not to be suggestive 
to all boys who desire to grow well proportioned, strong, 
and muscular? 



CHAPTER XXXII 

POISONS 

Poison Defined. — A poison is any drug, chemical, or 
other substance which, when taken into the body, tends to 
impair its health or destroy its life. Poisons differ in their 
characteristics and effects; a poison that acts in one way 
may sometimes act in a different way on a different in- 
dividual. While various classifications have been worked 
out for poisons, no well-defined division can be made 
between them. For convenience they may be treated under 
the following heads : corrosives, irritants, and narcotics. 

Corrosive Poisons. — Some poisons, alcohol, for instance, 
act slowly, while others produce immediate and fatal results. 
Those whose action is quick and destructive are called 
corrosive poisons. The most of these may be brought 
under two general classes, acids and alkalies. 

Acids. — Some of the common acids are sulphuric or 
oil of vitriol, muriatic, nitric, acetic, prussic, oxalic, and the 
so-called carbolic acid. Sulphuric acid is a heavy, thick, 
oily substance which chars or turns wood black when it 
comes in contact with it. Muriatic acid is used by black- 
smiths and tinners, is usually yellowish in color, and gives 
off the penetrating odor of chlorine. Nitric acid also has a 
strong odor, is usually yellow, and turns the skin- yellow 
where it touches it. Acetic is a much weaker acid than the 
others and is formed in ordinary vinegar. Prussic acid is a 
deadly poison in the concentrated form. It is found in 

298 



POISONS 299 

the leaves and pits of the peach and cherry, giving them a 
peculiar bitter taste. Oxalic acid is frequently found about 
the house in the form of crystals. It is used to clean wares, 
floors, etc., when dissolved in water. Carbolic acid is 
usually found in the crystalline form, sometimes in a semi- 
liquid or liquid condition. It burns and whitens the skin 
and mucous membrane. It may be detected by its odor. 

Antidotes for Acids. — If everyone were careful in keeping 
the bottles about the house labeled and in the proper place, 
there would not be much clanger from acid poisoning. 
Parents often leave bottles of these chemicals where small 
children can reach them or place them on the shelves, with- 
out any mark of identification ; as a result, they are taken by 
mistake. A special place should be provided for medicines 
of all kinds, and the bottles should be marked with the 
name of the medicine. In case of mistake, however, every- 
one should be familiar with the antidotes for the common 
poisons. 

It should be known by all that acids and alkalies are 
different in their chemical actions. By bringing an acid 
in contact with an alkali the two mutually destroy the cor- 
rosive actions of each other. The process of destroying the 
chemical properties of an acid or alkali by mixing the one 
with the other is called neutralization. The antidote for 
acid poisoning, then, is to give the victim something that 
contains an alkali. When one is certain from the presence 
of empty bottles or the symptoms manifested by the patient 
that he is suffering from acid poisoning, give him soda, 
powdered chalk, magnesia, limewater, or even pulverized 
plaster torn from the wall. Limewater is the best antidote 
if it is at hand. Soapsuds is also a good neutralizing 
agent. 



300 PHYSIOLOGY AND HYGIENE 

Alkalies. — An alkali is a substance that neutralizes an 
acid. Among the common alkalies are potash, ammonia, 
lime, and the old-fashioned lye leached from wood ash. 
Alkalies are strong caustics, have a greasy feel when brought 
in contact with the skin, and are used in the manufacture 
of soaps. They burn the mucous membrane, producing 
violent pains and vomiting. 

Antidotes for Alkalies. — The antidote for an alkali is a 
weak acid. This may ordinarily be found about the house 
in the form of vinegar, lemon juice, or acetic acid. Castor 
oil, linseed oil, and olive oil are also beneficial, inasmuch as 
they unite with the alkalies to form harmless soaps. After 
neutralization the affected parts should be soothed by a 
mixture of egg albumen, flour, and water. Remember that 
the action of a corrosive poison is quick, and no time 
should be wasted in producing vomiting. Results may be 
fatal before the poison can be thrown from the stomach. 
Apply the antidotes mentioned above immediately. Many 
a life has been saved by prompt and intelligent action. 

Irritant Poisons. — These include poisons whose actions 
are more prolonged, but which produce great pain, inflam- 
mation, or heat. They may be treated under three differ- 
ent divisions: metals, animal and vegetable poisons, and. 
gases. 

Metallic Poisons. — Among a large number of poisons of 
this class may be mentioned antimony, arsenic, mercury, 
copper, bismuth, iodine, lead, phosphorus, and silver. 
Antimony is found in tartar emetic and produces cramps, 
stupor, and vomiting. Arsenic occurs as a white powder 
and is an ingredient of Paris green, rat poison, green wall 
paper, and artificial flowers. Mercury is frequently used in 
the house as bichloride of mercury or corrosive sublimate. 



POISONS 301 

Copper is commonly found as blue vitriol and verdigris. 
It produces pain, inflammation, and vomiting. Bismuth 
is used as a medicine and produces symptoms much like 
those of copper. Iodine is found in tincture of iodine. 
Lead occurs in sugar of lead, paints, and water from lead 
pipes. It produces stupor and vomiting. Phosphorus is 
not a metal but is mentioned here for convenience. It is 
an ingredient of rat poisons and matches. Silver occurs 
in silver nitrate, or lunar caustic, and hair dyes. 

Antidotes for Metallic Poisons. — The important thing to 
do is to produce vomiting as soon as possible in order to get 
the poison out of the stomach. This may be done by giving 
an emetic, that is, a substance which will produce vomiting. 
Good emetics are magnesia, warm salt water, and mustard 
in water. If these will not bring the desired results, vomit- 
ing may be induced by forcing the finger down the throat. 
After the poison is driven from the stomach, soothing and 
healing substances should be applied. Among these may 
be mentioned mucilage, the white of an egg, flour and 
water, and strong teas. 

Animal and Vegetable Poisons. — We have stated at 
another place that fish and other meats, if allowed to stand, 
develop certain poisonous elements. Decayed vegetables 
likewise give rise to poisons that are virulent and deadly in 
their effects. Canned peas, tomatoes, and like vegetables 
are common sources of poisons. The presence of this class 
of poisons may be suggested by sudden and severe pains, 
followed by vomiting. Extreme thirst arises accompanied 
by headaches and convulsions. 

Antidotes for Animal and Vegetable Poisons. — As in the 
case of other irritants, the first object should be to get the 
poison out of the stomach. This may be done by giving 



302 PHYSIOLOGY AND HYGIENE 

emetics. When the stomach is emptied, mild soothing 
agents should be applied. Albumens, flour and water, 
strong coffee, and tea, are beneficial. The tea and coffee 
are stimulating and soothing in their effects. 

Gases. — The gases that are usually met with are carbon 
dioxide, carbon monoxide, hydrogen sulphide, coal gas, 
acetylene, and natural gas. 

Carbon dioxide is given off by the lungs and is sometimes 
foimd in deep mines and wells. Carbon monoxide accu- 
mulates in closed stoves and often explodes. Hydrogen 
sulphide is given off from certain kinds of mineral waters 
and is made in laboratories. Coal gas is the common manu- 
factured gas of our cities. Acetylene is made from carbide 
and is used like coal gas for lighting and heating. Natural 
gas issues from crevices and wells and is used in place of coal 
gas or acetylene. The most of these gases have character- 
istic odors which serve to identify them. Gas poisoning 
manifests itself by producing languor, stupor, and, finally, 
insensibility. 

Antidotes for Gas Poisoning. — The sufferer should be 
removed as quickly as possible to the open air. A stimulant 
in the form of weak ammonia gas should then be applied. 
Following these preliminaries, artificial respiration ought to 
be produced until the individual is revived or until it is 
evident that all life is extinct. Often it is desirable to carry 
the victim to some large well-ventilated room where the 
crowd cannot collect and prevent free access of air. It is 
well to remember that a clear head, quick hand, and patient, 
persistent treatment will restore respiration where confu- 
sion and excitement might result in death. 

Narcotic Poisons. — All of the narcotics are more or less 
poisonous in their nature, many of them being virulent. 



POISONS 303 

Their symptoms and antidotes have already been discussed. 
While the poisonous actions of the narcotics are slow, yet 
there are times when definite, rapid treatment is necessary. 

The Physician. — The preceding instructions in regard to 
antidotes and remedies have been given in order that young 
people may know what to do until the doctor comes. In a 
serious case of poisoning, not a moment should be lost in 
getting the physician to the side of the patient. The phy- 
sician has spent years in preparing himself to treat cases 
of this kind. 

The pallor of the cheek, the nature of the respiration, the 
throb of the heart, or the appearance of the eye may have 
no meaning to the ordinary observer and yet be full of sug- 
gestion to the trained senses of the physician. He should be 
implicitly trusted and his instructions faithfully followed. 



CHAPTER XXXIII 
TUBERCULOSIS 

By William Krauss, M.D., Ph.G. 

Nature of the Disease. — Tuberculosis is an infectious 
disease due to the entrance into the body and the develop- 
ment therein of a specific bacillus known as the bacillus 
tuberculosis. Before the disease can develop this bacillus 
must lodge at some point and multiply. This results at first 
in the formation of tiny nodules which are called " tuber- 
cules," from the Latin " tuberculum " i. e., a little knot. 

Bacteriology. 1 "Catching Diseases ." — In order to 
understand tuberculosis, we must have a clear idea 
of that group of diseases known as " infectious/' or 
" catching," diseases. Some diseases are not " catch- 
ing," but those that are may be communicated from 
one person to another in many, and often unsuspected, 
ways — one may " catch " such a disease by coming in 
contact with a person who has it, by eating food or 
fruit that he has handled, or by using some article 
that he has used. For instance, it is not safe to kiss 
one who has " a cold "or a sore throat, nor to use a 
handkerchief or a towel that has been used by a 
person so affected. 

Persons suffering from " a cold " are more apt to con- 
tract tuberculosis, or other " catching " disease than 

1 Bacteriology is the science which teaches about the little plants 
known as bacteria. Bacteriologists are scientists trained to understand 
bacteria and know how to study their properties. 

304 






TUBERCULOSIS 305 

are those with sound respiratory passages: hence, at 
such times exposure is especially to to be avoided. 

Formerly the diseases which pass directly from person 
to person were called " contagious," and those which 
could be transmitted by other means were known as " in- 
fectious." It is better, and bacteriologists now direct, that 
all transmissible diseases be called " infectious.". 

How Diseases are Spread. — Every infectious disease has 
at least some methods of spreading peculiar to itself. If 
the substance that carries a disease from one person to an- 
other were an inanimate poison, 1 like rat poison, arsenic 
or carbolic acid there would not be enough to go round. 
If you were to try to sweeten 100 cups of coffee with one 
or two pieces of sugar you certainly could not taste it in 
the coffee. If enough poison to kill a person when put into 
one cup of coffee were put into 100 cups, to be taken by as 
many persons, it would not make even one sick. And yet 
this material which causes us to become ill with a disease is 
a poison. 

Now, how does it happen that in the whole world about 
every tenth person who dies loses his or her life from tuber- 
culosis? There must be great quantities of this tuberculosis 
poison in the world. Yes, that is true, but if all the tuber- 
culosis poison in the world could be killed at one time there 
would never be another case of tuberculosis. Killed? 
Yes. It is because it has life that it can multiply so rap- 
idly. Just as the yeast plant grows by budding and bud- 
ding so that in one day there are millions of times more of 
it than at the beginning, so the tuberculosis plant — for it 
is a plant — will multiply enormously when it gets into the 
body. How do we know this? 

1 Not endowed with life. 



306 PHYSIOLOGY AND HYGIENE 

Inoculation. — We can poison a guinea pig, weighing 
about two pounds, by injecting into its body a very little 
of the spittle from a person having consumption. 1 In 
the course of several weeks this consumption material will 
have multiplied so much that the guinea pig dies from the 
disease, and now there is enough consumption poison in its 
little body to start the disease in thousands of guinea pigs. 
If the spittle is cooked before it is injected it will take a 
great deal of it to even make a guinea pig sick, although 
the cooked spittle is just as poisonous as the raw, but the 
cooking has destro} r ed the power of multiplying. Though 
enough of the cooked spittle be used to make the pig sick 
it will get well, and now it will take more of the raw, live 
spittle to make it sick than it did before. The pig has 
acquired a small degree of " immunity," that is, it has 
developed some ability to resist catching the disease. 

Now, although the first pig died it was able by the cells 
of its body to kill myriads of the tubercular bacilli but it 
could not kill them all. Several days would be required 
to show that the animal was sick, for in the beginning its 
resistance would enable it to keep pace with the increasing 
infection, but finally the multiplication would become so 
rapid that in spite of the millions of bacteria killed the 
animal would succumb. The period after infection during 
which no symptoms appear is known as the period of in- 
cubation. 

Bacteria. — The little bodies which so multiply as to 
give tuberculosis to millions of people are called bacteria. 
We often hear people call them germs, and though there 
is a definition of germ under which they might be included 
it is better to call them by the specific name bacteria, as 

1 Consumption is tuberculosis of the lungs in an advanced stage. 



TUBERCULOSIS 307 

that separates them from other organisms covered by the 
broader definition. 

Bacteria never grow any larger, they just multiply. At 
first they seem to elongate, but before they are twice as 
long as they were at the beginning they break in two, and 
then there are two short ones to repeat the process. Each 
time their number is doubled. Did you ever try to work 
out the example of the blacksmith who said he would not 
charge for the horseshoes but would charge only for the 
nails used; one cent for the first nail, two for the second, 
four for the third, and so on? The poor owner worked 
out the problem and found his job of horseshoeing would 
cost him more than all the money in all the banks of the 
state. In the same way, each generation of bacteria in- 
creases twice as fast as the last one. Now, if there were 
but one generation a month they would not be formidable. 
But a single consumptive may spit out over five billions 
of living bacteria in one day. 

Different Kinds of Bacteria. — Now, as stated before, 
these wonderful little multipliers are plants, just as yeast 
is a plant. Each one is a complete plant and so small that 
10,000 of them, in a straight line, can swim crosswise 
through the eye of a cambric needle. And these little 
plants do swim, some of them. It is difficult to make the 
tuberculosis plant swim, but many others do. If we watch 
the typhoid fever plants under a microscope which mag- 
nifies 1,000 diameters, or 1,000,000 areas, we can see them 
squirm and swim about like tadpoles. Each infectious 
disease has a special kind of plant that is different from all 
other plants. Some differ from others as much as a pine 
tree differs from a rose bush. Others differ so little that 
we can tell them apart only by putting them to work. 



308 PHYSIOLOGY AND HYGIENE 

And what workers these little plants are! Some of them 
curdle milk and others make hard cheese out of it. Dif- 
ferent kinds of cheese owe their flavors to the peculiar 
plant used in making cheese. Some of them make other 
plants grow. If you dig up cow peas you can find on the 
little roots near the surface very small knots and these are 
full of bacteria, They catch the nitrogen from the air and 
give it to the cow peas to live on. We know an endless 
variety of these microscopic plants that are useful in many 
ways. In this respect they do not differ from the higher 
forms of plant life. Some furnish food, others flowers, 
others, like the deadly nightshade, make poison. 

Some bacteria live upon dead matter and cause it to dis- 
integrate or decompose. Commonly we call it "rotting." 
Nothing could rot if it were not for these busy little plants. 
They utilize what they need to live upon and the rest is 
" decomposed" matter. They rot dead plants and stalks 
and thus prepare them to be plowed under in the spring, 
making them useful as fertilizers by causing them to give 
back to the earth what they had to take from it during life. 
They rot dead animal matter and cause it to attract higher 
forms of life that feed on decomposing flesh, and thus pre- 
vent its cumbering the earth. Bacteria which live upon 
dead matter are called " saprophytic " bacteria, or sapro- 
phytes. 

Kinds of Plants. — The bacteria have no chlorophyll, or 
plant green, as the higher orders of plants have. With the 
possible exception of some parasitic plants, as mistletoe, it 
is a fact that plants having this plant green, or chlorophyll 
can live upon substances from the mineral kingdom; while 
bacteria which are without the chlorophyll must sustain 
themselves from the animal or vegetable kingdom, from 



TUBERCULOSIS 309 

something that is alive; hence, as parasites, or from some- 
thing that has been alive; hence, as scavengers. Those 
which thrive on man and other living animals are the ones 
which produce disease. They need the substance of our 
body cells to live upon, and, living on them injure them. 
The disease producing bacteria are known as " pathogenic " 
bacteria, and to this class belongs the tubercle bacillus. 

Pathogenic and other bacteria can be made to grow arti- 
ficially by planting them on suitable " culture media," 
that is, planting them on something that they can live on 
for a time. This fact is largely taken advantage of in 
studying them. Most of them, especially the pathogenic, 
must be kept at the body temperature in what is known as 
an " incubator." These artificial growths can be trans- 
planted as often as we wish, and each new culture or growth 
shows them massed together in such numbers that they 
form a patch that can be seen and from the appearance 
of the patches we can tell them apart. Closely allied species 
of bacteria can be tested out by taking some of the culture 
and inoculating an animal to see what kind of sickness it 
produces. 

General Characteristics of Bacteria. — Some bacteria pre- 
fer one kind of a body cell, some another kind, and still 
others take anything they can get. They can live in the 
blood after they have injured a person, that is, after the 
cells have become weakened in their fight against the bac- 
teria. And they do fight, these body cells. If they did 
not, the human race would have been extinct long ago. 
Some bacteria poison the red corpuscles of the blood, but 
they may be eaten by the white blood corpuscles, which is 
one way of fighting disease. Some bacteria get into the 
mucous membrane of the throat and stay therej but they 



310 



PHYSIOLOGY AND HYGIENE 



are so busy making poison that the whole body becomes 
poisoned and the little patient dies, unless he is given anti- 
toxin, lots of it, and, as early as possible. These bacteria 
are the diphtheria bacilli, and the disease is diphtheria. 

Antitoxin can be made only for such diseases as are pro- 
duced by bacteria which make poison in " cultures." 
There is no antitoxin for the tubercle bacillus, because it 



#3 •« •£>£% 9 



N 



y-m ft* 



1© 

11 




Fig. 120.— Various Kinds of Bacteria. 

1, cocci: 2. bacilli; 3, bacilli with swimming tails (flagella); 4, spirilla; 5, bacteria 
with capsules; 6, tetrageni; 7, diplococci; 8, bacilli with spores; 9, streptococci; 
10, vibrios; 11, bacilli in chains; 12, molds; 13, flowering molds; 14, yeast. 



sets free its poison in its fight with the body cells, and to 
be made harmless this poison must be dissolved or de- 
stroyed. 

We know the bacteria of typhoid fever, of influenza, of 
pneumonia, cholera plague, erysipelas, and a great many 
other diseases. Some diseases are produced by plants 
higher up in the scale of life than bacteria, such as yeasts 
and molds. 

Bacteria have different shapes. Some are round like 



TUBERCULOSIS 311 

extremely small shot, others are longer like little rods; this 
is what the word bacterium really means, but we have 
come to apply the name to all forms. When the rods are 
longer than twice their width, they are named bacilli. 
Curved ones are spirilla, and there are still other varieties. 
(Fig. 120.) i 

The Tubercle Bacillus. — This is not really a bacillus 
at all. If we want to be very particular we must call it 
corynebacterium. That is too much of a name, and because 
it was called bacillus by its discoverer, Prof. Robert Koch, 
we still use this name in honor of the discoverer. It is also 
known as the bacillus of Koch. 

This bacillus, the discover}' of which was reported in 
1882, is a very slender rod, several varieties of which are 
known. The most common are the bovine tubercle bacillus, 
which is more dangerous to animals and less dangerous to 
man, and is shorter than the " human " bacillus. 

Both are dangerous to human life, but the latter far more 
so. The tubercle bacillus cannot be seen unless we dye it 
a very special way discovered by Koch, which is the reason 
he was the first one to see it. When dyed it can be seen 
under a microscope with a power as low as 500 diameters, 
but its peculiar outline can be studied only under higher 
powers. As it is usually dyed red, all the rest of the 
picture being colored blue by a contrast stain, it appears 
like minute fragments of red silk fiber, and in another form 
like a string of very small red beads (Fig. 121). The hu- 
man bacillus is from 1 q 00 of an inch to 50 \ of an inch 

1 Xot all transmissible diseases are due to bacteria. Many are caused 
by little animals, belonging mostly to the class of "protozoa." Most 
of the protozoa are transmitted by stinging insects. Malaria protozoa 
are injected by a certain species of mosquito; some diseases are trans- 
mitted by ticks, stinging flies, fleas, etc. 




312 PHYSIOLOGY AND HYGIENE 

long, and from 50 ooo to 20000 of an inch in thickness. 
Over 16,000,000 can be placed side by side and end to end, 

in a single layer, on a 
s 0r&f postage stamp. 

Biological Character of 
the Tubercle Bacillus. — 
Although it takes blood- 
heat and body cells or 
culture media to enable 
•^ *&*'$. & ■ the tubercle bacilli to 
^3£L " "^"^ multiply, they resist ev- 

Fig. 121. -Tubercle Bacilli in Sputum, ery known degree of cold 

Notice different shapes, and " Roman numer- without being killed, and 
al " arrangement; the large bodies are . , _ -, 

white blood corpuscles, degenerated. Can live OUtSlde OI the 

bod)^, in darkened places, 
for months without losing their virulence. 1 Diffuse day- 
light kills them in a few days, and direct sunlight will kill 
them in a few hours, if the layer is not too thick. This 
teaches that we should let daylight freely into our dwell- 
ings, shops and factories. 

While dry tubercle bacilli will stand boiling tempera- 
ture for an hour and live, a liquid, like milk, containing 
them must be heated to 150 degrees F. for an hour, or boiled 
for at least fifteen minutes, in order to kill them. They are 
easily killed by certain poisonous chemicals known as dis- 
infectants. 2 Sputum or spittle from a consumptive is thick 
and sticky and does not easily mix with disinfectants. The 
best disinfectant to use is formalin, one part of formalin to 

1 Virulence is ability to poison ; virulence may be much weakened 
by environment. 

2 Disinfectants are agents that destroy bacteria, or render them 
harmless. 



TUBERCULOSIS 313 

six parts of water, or pure carbolic acid mixed with twenty 
times as much water. There must be at least twice as much 
disinfectant as material to be treated, and they must be well 
stirred together and left for two hours to give the disinfectant 
time to kill the bacilli before being thrown out. Many so- 
called disinfectants are worthless; none can do good unless 
in prolonged actual contact with the bacteria or the ma- 
terial containing them. The " smell " of a disinfectant is 
entirely without effect. 

The Lesson of the Biology of the Tubercle Bacillus. — 1. 
One may have the bacilli of tuberculosis in the sputum 
without knowing it. Therefore no one should spit where 
the sputum can be carried by flies, or get on the shoes, or 
clothing, or dry up and be blown about as dust to be in- 
haled or wafted on food or into drink. The spittle of a per- 
son having tuberculosis is the most dangerous thing about 
him; but it matters not how the bacilli are discharged from 
the body, flies will prove efficient agents in distributing them. 

2. The nasal discharges should be received into a hand- 
kerchief that can be boiled, or a rag or piece of gauze that 
can be burned. One should sneeze into a handkerchief, 
and not into another's face. If 3^ou have a cold use a piece 
of gauze when blowing the nose and have the gauze burned. 
If you have a cough use gauze to receive the expectorations 
and have the gauze burned. 

3. Do not put anything into your mouth except food 
and not that if it has been handled by unclean hands, or 
has been touched by flies, or has been in another's mouth. 
Fruits that have been exposed to the dust of the streets 
are dangerous, unless carefully cleaned before they are eaten. 
Candies exposed to the dust of the street and to flies can 
not be cleaned beyond danger except by long cooking. 



314 PHYSIOLOGY AND HYGIENE 

4. Do not swap candy and chewing gum with your play- 
mates and do not kiss them on the mouth. Don't put lead 
pencils or slate pencils into your mouth, they will write 
better if they have never been wet with saliva. 

5. Be cleanly in your habits; dirt may contain bacteria 
of all kinds; wash your hands and clean your nails before 
eating; keep your teeth clean with a toothbrush of your 
own. 

6. Always remember how tubercle bacilli can be killed; 
let God's pure, cleansing sunshine into the house, breathe 
fresh air, avoid damp, dark, musty places, and keep the 
house well ventilated, especially your sleeping quarters. 

Tuberculosis as a Disease. — Tuberculosis is as old as 
history. Tubercle bacilli and evidences of tuberculosis 
have been found in Egyptian mummies, the oldest relics of 
civilization. One thousand years before Christ the disease 
was described so clearly that there can be no doubt that 
the people in this early period recognized it as a distinct 
disease. 

There are proofs that we will allude to later that every 
person over twenty years of age has probably had tubercu- 
losis at some time in life without having known it. There is 
no other disease which claims so many victims. All over 
the world one out of every seven or ten dies of tuberculosis. 
The victims who are going to die of the disease have an 
extraordinary pallor of the skin. Owing to this fact, and 
because the disease claims so many victims it is known as 
the " Great White Plague." In the census year of 1900, 110,- 
000 persons died in the United States of tuberculosis, equal 
to nearly two for every thousand living persons, and equal to 
110 deaths from tuberculosis out of each 1,000 deaths from 
all causes. In other words, whenever 100 persons died 11 




Fig-. 122.— Comparative Death Kates. 



TUBERCULOSIS 315 

of the deaths were from tuberculosis. In some states the 
deaths from tuberculosis make up over fifteen per cent of 
all the deaths. 

The following diagram, taken from the United States cen- 
sus of 1900 gives the eight principal causes of death, per 
1,000 deaths, from all 
causes. We see that 
there were 110 deaths 
per thousand due to 
tuberculosis (Fig. 122). 
Appalling as these 
figures are it must be 
remembered that we 
know more about tu- 
berculosis than we did 
ten years ago, and we need only to heed the lessons of these 
pages to help reduce this frightful mortality. We shall 
later see to what extent, and how tuberculosis is curable. 

Cost of Tuberculosis. — At present, the average life of a 
consumptive, including those who get well is five years. 
During only a part of this time they can earn a little money 
by light work; later they become a burden on those who 
have to care for them. 

Dr. Price has shown that the loss to a community of an 
average wage-earning man is $8,500; that the State of 
Maryland lost 900 such men in one year from tuberculosis, 
thus losing to the state in one year wage-earning capacity 
of 17,650,000. The loss to the families in broken hearts, 
sorrow, want and neglect cannot be estimated in dollars 
and cents. 

How the Tubercle Bacillus gets into the Body. — The 
" portals of entry " of the tubercle bacillus are similar to 



316 PHYSIOLOGY AND HYGIENE 

those of other bacteria. The most frequent route is through 
the nose and mouth, either by inhalation or by contami- 
nated food and drink. We must guard against infected or 
contaminated food, unclean eating utensils, cups, glasses, 
napkins, towels and clothing. 

We should not live in unsanitary houses, nor have car- 
pets, matting or other dust-catching floor covering. Rugs 
and hangings should be frequently changed. Rarely the 
bacillus enters through the broken skin and may then reach 
distant parts of the body; more often it gives rise to two 
forms of skin tuberculosis. 

Route of Travel. — The route to the lungs is often a direct 
one through the respiratory tract by inhaling the spray of 
some one coughing or the dried sputum in the form of dust. 
On its passage the bacillus meets many obstacles; it may be 
arrested by the sound, moist mucous membrane of the nose, 
throat or windpipe. Persons suffering from " cold," grippe, 
diphtheria, measles, scarlet fever, bronchitis and pneumonia 
have this defense impaired, and are more apt to become 
infected with tuberculosis. Such patients should not be 
shut into a hot, close room; they should be well wrapped 
up and allowed to breathe air from an open window. Of- 
ten the lungs are reached in an indirect way; the bacilli may 
pass through the lacteals of the intestine (which see) and 
travel in the blood or lymph until they reach the " dead 
space " in the top of the lungs, where, owing to the bellows- 
action of the lungs, the circulation is very much slowed, and 
the bacilli have time to lodge. 

Sometimes the bacilli lodge in the " adenoids," in the 
tonsils, or the bronchial lymph glands in the chest. In 
"mouth-breathers" this route is far the most direct. Chil- 
dren having adenoids are generally mouth-breathers. Ev- 



TUBERCULOSIS 317 

ery child should be examined by the family physician and 
if adenoids exist they should be removed. "Adenoids" 
are enlarged lymph nodes in the back of the nose; they pre- 
vent air from passing freely; they favor the deposit of for- 
eign matter and also favor the direct route to the lungs. 
As stated, the direct route to the lungs is the most danger- 
ous. Next in order is by the air through the nearest lym- 
phatics (adenoids or tonsils). Then comes the route 
through the alimentary tract and by way of the lac teals 
through the lymph and blood. We thus recognize three 
ways the bacilli infect us: 1. Through the respiratory 
tract. 2. Through the alimentary tract. 3. Through the 
skin. In each case they may reach the lungs. It must not 
be supposed that the lungs are alone the seat of the disease ; 
it is only more frequent there because the lungs resist the 
disease the least. 

How Tuberculosis Affects the Body. — Tuberculosis may 
attack the body at any age; some ages favor certain sites. 
Over nine-tenths of the sufferers from tuberculosis die of the 
lung form, or consumption, but even these have the disease 
in other organs before they die. It may locate in the 
upper air passages, in the nose, throat and bronchial tubes, 
in the mouth (rarely), in the esophagus, in the small and 
large intestine, in the liver, spleen, kidneys, the urinary 
organs, the brain, the bones and joints, in the skin, and even 
in the heart muscles. The tonsils, bronchial glands, lungs 
and intestines are the most usual seats of the disease. 

Consumption is an advanced form of tuberculosis of the 
lungs. It may be acute or " galloping consumption" or 
very chronic, lasting many years. 

Tabes mesenterica is tuberculosis of the intestine in young 
children. 



318 PHYSIOLOGY AND HYGIENE 

Hip disease is tuberculosis of the hip joint. 

White swelling is tuberculosis of the knee joint. 

Pott's disease is tuberculosis of the spine. 

The brain fever of children is frequently tuberculosis of 
the brain. 

Lupus is tuberculosis of the skin. 

Scrojida is tuberculosis of the lymph glands, usually of 
the neck. The ulcerating swellings of the neck are scrofula. 

Adenoids are enlarged glands in the upper air passages, 
and are often the seat of tuberculosis. They are rarely 
large without being swollen. 

Mode of Spread. — We have learned that tubercle bacilli 
do not multiply outside of the body, but there are many 
ways in which they can be kept alive and carried about. 
We know about the contaminated food, the dust and the 
fabrics. Among the worst carriers of tuberculosis are house 
flies. This is a most filthy insect. Born in the manure 
heap, it eats everything without discrimination, from • a 
nauseous puddle, sputum, blood, pus, decomposed meat, 
etc., and then it comes m through the window and plants 
its sticky, hairy, filthy legs into your pastry or stewed fruit. 
Flies eat sputum, and a single fly speck may contain five 
million live tubercle bacilli. Flies in hospitals where tu- 
berculosis is treated, when ground up and injected, will 
infect guinea pigs. What good is there in placarding a 
house where diphtheria and scarlet fever exist when flies 
are permitted to pass through the open window 7 into the 
next house ? Flies from diphtheria houses have been made 
to walk over gelatine (on which diphtheria bacilli grow) 
and in their tracks millions of diphtheria bacilli would de- 
velop. Experiments also show that flies carry typhoid 
fever, pus bacteria, scarlet fever, cholera plague, and other 



TUBERCULOSIS 



319 



diseases. To prevent this houses should be screened, 
manure piles kept away from the dwellings, and sticky fly 
paper placed in the rooms; poison fly papers permit the 
flies to fall about the room or into the food. 

The Role of Domestic Animals in the Spread of Tubercu- 
losis. — Cats and pet dogs carry all kinds of infection in 
their furry coats. All domestic animals, except goats, can 
have tuberculosis. Rats are scavengers, not more partic- 
ular than flies, and may contaminate food. They are the 
carriers of plague which they transmit to man by means 





Fig. 123.— Spit cups. 



of their fleas. Body parasites and ants carry disease. The 
lesson is, do not let sputum get on anything from which it 
can be transmitted by " carriers." Consumptives should 
use specially prepared cups; there is a pocket form also. 
Spit cups can be disinfected or burned (Fig. 123). 



CHAPTER XXXIV 

"CATCHING" TUBERCULOSIS 

Milk. — Behring claims that all human tuberculosis 
comes from drinking milk from tuberculous cows, the ba- 
cilli passing through the lacteals and later getting into the 
lungs or other organs. The weight of opinion is that this 
is only a possible mode of infection. No one should drink 
milk that comes from a cow that has fever. All dairy cat- 
tle should be tested w T ith tuberculin. 1 We have seen that 
bringing milk to the boiling point will not destroy the tu- 
bercle bacilli. Fortunately a cow has to get very sick 
before bacilli get into the milk, and the thermometer test 
above given is quite safe. It is especially important that 
milk fed to infants be free from tuberculosis. The only way 
to find this out is to test the cow. 

Meat. — If tuberculous cattle are killed early in the dis- 
ease, their boiled flesh may be eaten, provided it is thor- 
oughly boiled. We have learned that the muscles are the 
last tissues affected by tuberculosis, and the length of time 
that meat is boiled to have it "well done" makes it safe 
food. We should never eat raw or rare beef unless it has 
been " inspected." Not only may it cause tuberculosis, but 
it may also transmit the beef tapeworm. 

Water. — The water of small streams and superficial 
wells may become contaminated with tuberculosis. The 

1 An injection which causes a high fever in tuberculous cows. 

320 



"CATCHING" TUBERCULOSIS 321 

danger of this is not as great as contamination with typhoid 
fever, dysentery and certain other diseases. Particular 
care should be used to have the water used about dairies 
perfectly pure. 

Servants, Mechanics and Laborers. — Too little attention 
is paid to the state of health of those who supply our needs. 
House servants who are in poor health should be examined 
by the family physician, and be dismissed, if there is even 
a suspicion of tuberculosis. Butchers, tradesmen, clerks 
and delivery men may contaminate articles, if they have 
tuberculosis, or if the disease exists in their homes. It is a 
false sense of sympathy that permits such persons to be a 
menace to the family. 

Predisposing Causes of Tuberculosis. — By this we mean 
the various conditions which make us susceptible to tuber- 
culosis. 

Age. — No age is exempt, although the disease is most 
common between the ages of twenty and thirty-five years. 
This is the most productive age, and this circumstance 
makes the economic aspect of tuberculosis all the more 
important. 

Sex. — The sexes are nearly equally liable to the disease. 

Race. — The negro is twice as susceptible as the white 
man, as shown by the following table (Fig. 124) . The Great 
White Plague has exterminated far more Indians than the 
bullets of the "pale faces." The death rate for nine reser- 
vations where actual figures are given shows the average 
proportion of deaths from this disease to have been sixty-six 
per cent, of all the deaths recorded. The records of deaths 
of Japanese and Chinese in portions of the United States 
where accurate records are kept gives a death rate much 
higher than that among negroes. 



322 



PHYSIOLOGY AND HYGIENE 



Locality. — The disease is more frequent and fatal in 
low, damp localities than in high, dry climates. The aver- 
age rainfall has much bearing on the prevalence of tuber- 

MORTALITY FROM TUBERCULOSIS, 1909 

Rate per Hundred Thousand 
White and Colored 




white [ 



Fig. 124— Mortality Table by Thomas J. Brown. Klebs, Tuberculosis. 



"CATCHING" TUBERCULOSIS 323 

culosis. Uniformity of temperature and the greatest 
amount of sunshine favor the cure of the disease. It is 
worse in the subtropics than in the extreme North. Among 
the Eskimos it was formerly unknown and it is rare among 
them now. The harm of cold weather will be taken up 
later. Tuberculosis is also more prevalent in densely 
populated quarters in large cities than in the country. In 
some states the ratio is two to one. 

Heredity. — The old idea that tuberculosis is hereditary, 
that is, that we are born with it, is wrong. There are only 
certain conditions that make the children of tuberculous 
parents more susceptible. The consumptive mother cod- 
dles and kisses the child, prepares its food and tastes it; 
later, the child plays about on the floor and inhales the dust ; 
it touches everything and puts into its mouth everything 
it can. The mother probably adheres to the old idea that 
a hot, close room is good for her cough, and the child is 
made a "hot house plant." It was formerly the idea that 
consumptives must not be told of their disease because it 
might frighten them, and so they were ignorant as to the 
danger and methods of spreading the disease to others, and 
so, in a variety of ways, the child was constantly exposed 
to infection. 

v Szaboky collected statistics from 1,456 tuberculous and 
1,433 non-tuberculous parents from which he determined 
that hereditary predisposition was of equal importance 
with acquired predisposition. The most that can be said 
of " heredity" is that it is an inherited predisposition, 
coupled with environment. 

Susceptibility. — What is susceptibility? An animal is 
susceptible to disease when it easily falls a victim to it. 
To tuberculosis, for instance, the most susceptible animals 



324 PHYSIOLOGY AND HYGIENE 

are pet rabbits and guinea pigs, cattle, especially the milch 
cow, and the pig. Dogs and horses are less susceptible. 
Such natural susceptibilities are racial, and, to this extent,, 
inherited. Even in these the susceptibility is variable. 
To some extent, also, it is a question of the virulence of the 
strain of bacillus. Cattle tuberculosis is transmitted to the 
human species with more difficulty. 

It is certain that one individual readily succumbs even 
after a slight exposure, and that another may be infected 
often and still escape active sickness; the latter seems to be 
always able to kill the bacilli by means of his normal de- 
fenses. An individual may be more susceptible to one 
disease than to another. The "weakling" easily falls a 
victim to an} r disease. Since tuberculosis is by far the 
most prevalent disease, susceptibility to it is simply more 
common. A cured consumptive is more liable to re-infec- 
tion than lie was to the original infection. The children of 
weak and puny parents are more susceptible, and for this 
reason weaklings should not marry. 

By recognizing tuberculosis early and by observing hy- 
gienic rules we can overcome susceptibility very much, 
whether it is inherited or acquired. We should discourage 
the doctrine of heredity because of its depressing and harm- 
ful effect on those concerned. The weak person has a 
better chance for life and health now than he ever had 
before. 

Constitution. — From the foregoing it follows that we 
must look to the improvement of the general health in 
every way. If there are evidences of imperfect develop- 
ment the conditions must be improved. The person must 
take gymnastic exercises — but not in the close and dusty 
room. Such exercises as will expand the chest and raise 



"CATCHING" TUBERCULOSIS 325 

the stooped shoulders should be gone through, such as 
stooping to touch the toes without bending the knees, 
climbing a rope, etc. All exercises should, when possible, 
be taken under the direction of an instructor and with the 
advice of a physician so as not to overexert a weak heart 
or weak lungs. 

Other Diseases as Predisposing Causes. — We know that 
certain respiratory diseases predispose to tuberculosis. 
Among other predisposing diseases are malaria, various 
blood poisons, typhoid and rheumatic fever, diabetes, 
epilepsy and insanity. Injuries lead to diseases of the 
bones, joints and spine, because tubercle bacilli prefer to 
lodge where there is an old inflammation. It often happens 
that tuberculosis comes on with chills and fever, with 
sweating, or there may be a prolonged spell of fever like 
typhoid fever; in fact, such cases have been mistaken for 
malaria or for typhoid fever. Both these diseases can be 
recognized by examining the blood, which should be done 
in every case. 

Alcohol and Tobacco. — Alcoholic drinks, when taken 
habitually or frequently, predispose very much to tubercu- 
losis. Tobacco, and especially cigarettes, when the smoke 
is inhaled, tend to irritate the respiratory passages and also 
to weaken the body and thus predispose to tuberculosis. 

Occupation. — Many occupations, especially those as- 
sociated with the inhalation of poisonous dust claim many 
victims. The worst of these are file cutting, brass working, 
and work in certain chemical factories. Dentists are very 
much exposed to infection. Those working in damp, un- 
ventilated places, and poor laborers living in unsanitary 
houses furnish a large number of cases. 

Exciting Cause. — All diseases have predisposing and 



326 PHYSIOLOGY AND HYGIENE 

exciting causes. Any of several tilings may be predispos- 
ing causes but there is only one exciting cause of tubercu- 
losis. No one can have this disease unless the bacilli grow 
in his body. After entering the body the bacilli may re- 
main dormant for many weeks, months or years. Then 
something happens in the way of a predisposing cause, either 
another sickness, trouble, grief, or any of the conditions 
mentioned, and the normal resistance is reduced, and now 
we have susceptibility. 

When the tubercle bacillus first gets into the tissues it 
excites an inflammation of such low grade and in such a 
tiny spot that it passes unnoticed. The tissue cells multi- 
ply around it (see page 5 of this book) and the tubercle 
bacillus is walled in. Gradually the cells surrounding it 
are poisoned and break down. Now, the cells a little farther 
off take up the fight, both cells and bacilli multiply, and 
now the white corpuscles of the blood (see page 82) are 
attracted to the scene. This is the way the body mobilizes 
its defenses. The inflammatory irritation is the alarm 
signal, and the white corpuscles of the blood escape from 
the walls of the blood-vessels in the neighborhood and rush 
to the defense. Just as firemen rush to a fire, so these little 
cells are trained to run up, and a battle ensues between 
them and the bacilli. At first they fight only with chemical 
weapons, just as firemen do. (Every invention is copied 
from Nature.) The bacilli send out a toxin, and the cor- 
puscles send out antitoxin. If the toxicity of the bacillus 
is too great the white corpuscles cannot get into the neigh- 
borhood; they act as if they were afraid. The poison 
secreted by the bacilli holds them in check at the outskirts 
of the fortifications. But if the tubercular toxin is not 
too strong the white cells, or corpuscles, as soon as they 



"CATCHING" TUBERCULOSIS 327 

have neutralized the toxin, throw themselves upon the 
bacilli and devour them. 

After the bodv cells have won the battle, the rem aini ng 
bacilli are so injured that they die, and the tissue cells dis- 
pose of them. If the bacilli win the fight, they either mul- 
tiply in the neighborhood or in other parts of the body, where 
they may have been carried by a foolish, impetuous white 




Fig-. 125.— Lung- tubercle, showing- giant cell formation, magnified section. 

corpuscle which has swallowed one too poisonous for it, in 
consequence of which it dies and the bacillus is set free. 
Wherever it lodges it causes the growth of a tiny, grayish, 
glistening, roundish new formation of previously multiplied, 
but now dead, body cells, which is the nodule or tubercle 
(Fig. 125). We will follow this further under " curability.' y 



CHAPTER XXXV 

RECOGNIZING AND CURING TUBERCULOSIS 

Signs and Symptoms of Tuberculosis. — The early signs 
of .tuberculosis are not often characteristic and simply 
amount to being "out of sorts/' weak, puny, with a little 
fever, perhaps some cough — but this is not necessarily an 
early sign — loss of appetite and a tendency to getting tired. 
Such symptoms should not frighten us because they may 
be due to some other malady or merely a "run-down con- 
dition." In any case, in this stage, it is usually curable. 
At this time a careful doctor. ought to be consulted, one 
who will take time to make a thorough examination. Don't, 
under any circumstances, take any "patent medicine" or 
anything your neighbor recommends. Never take any 
medicine for any disease without a diagnosis. No medi- 
cine is harmless unless prescribed by a doctor who knows 
or can judge your constitution, and can understand what 
particular medicine should be used. The worst thing about 
taking medicine suggested, by just anybody, is it delays 
proper treatment too long and the disease is not recognized 
till it is too late. Many lives are sacrificed every year by 
this too-lateness. More than half of those who die of tu- 
berculosis do so because they do not heed this lesson. 
There is no consumption cure, and those who claim to have 
one do not tell the truth. They are unscrupulous persons 
who simply want your money. They are worse than bur- 
glars, because burglars do not always injure you. Do not 

328 



RECOGNIZING AND CURING TUBERCULOSIS 329 

be deceived. Insist upon knowing the truth, else you will 
be like the ostrich which sticks its head into the sand in 
moments of danger. AVe should recognize tuberculosis 
early for two reasons: 1. Because the sooner it is recog- 
nized and comes under expert observation the more certain 
will be the beneficial results. 2. Because the tuberculous 
individual who goes about in the circles of the well, without 
knowing his condition, is apt to infect others. The careful, 
conscientious consumptive, who follows the directions of 
his doctor, is no menace to the health of those about him, 
and he has the best chance to get well. 

Bear this lesson in mind : when the annoying little cough, 
the poor appetite, the slight fever, the weakness, the flushes, 
the morning sweat, or any several of these symptoms have 
lasted a few weeks at most, it is time to go to your phy- 
sician and ask for a thorough examination. It may frighten 
you, but if you know the truth you may be cured, which is 
better than waiting till you have it dawn upon you that 
your case is hopeless. 

Do not bury your head in the sand like the ostrich, but 
resolutely go to your doctor and learn the truth. The 
doctor may be able to relieve your anxiety by finding your 
trouble to be something else, and give you a medicine that 
will make you well. 

It has been suggested that the head of the family take 
the temperature, the weight and waist measure of those in 
the house from time to time. A persistent rise of the tem- 
perature after meals is a suspicious sign. These precau- 
tions will tend to keep the family well, and the disease does 
not often attack those in vigorous health. If it does the 
first sign will probably be blood-spitting, especially after 
exercise. This may amount to nothing, but we should put 



330 PHYSIOLOGY AND HYGIENE 

the responsibility on the family physician. If the spittle is 
frothy, bright red and floats upon water, it comes from the 
lungs. 

Toxin of the Tubercle Bacillus. — The toxin, spoken of 
in another chapter, is a soluble poison thrown out by the 
bacillus which goes into the circulation and is distributed 
all over the body. This is the cause of the fever, the 
sweats, the poor appetite, the weakness and other symp- 
toms mentioned. 

It destroys, by chemical action, the little red corpuscles 
of the blood and produces anaemia, which makes the sufferer 
pale. It weakens the muscles, the nerves, the brain and 
the heart, although the bacilli are located in a small spot 
elsewhere. This toxin is made by the bacilli in their fight 
against the body. Fighting is also done by the tissue cells 
which require the breaking up of the bacilli. This is why 
we cannot make an antitoxin for it, the toxin being sep- 
arated in the living body. 

The Curability of Tuberculosis. — In sanitoria 1 where 
consumptives are in the care of a specialist, taking the 
average for all stages of the disease, they give negative re- 
sults in from twelve to thirty per cent, of the cases treated, 
and positive results in from sixty to eighty per cent, of the 
cases. The positive results include cases of improvement 
without actual cure. Many patients leave after improve- 
ment and the final results are not known. Some of the 
cases cured lapse into bad habits and carelessness, and later 
relapse. In the earliest stages of the disease it is arrested 
in most cases. 

Of those known to have consumption and who neglect 
themselves over two-thirds die of the disease. Post-mor- 

1 Special hospitals, in this case for consumptives. 



RECOGNIZING AND CURING TUBERCULOSIS 331 

tern examinations of the lungs of persons who have died in 
hospitals of other diseases show that, after the age of 
twenty, probably every person has had a "touch" of 
tuberculosis — which has healed without ever having been 
suspected. This shows that tuberculosis is one of the most 
curable of all diseases. The above fact has caused a Vienna 
professor to make his famous remark that "eventually 
every one has a little tuberculosis." On the other hand, 
practically all cases of so-called "galloping consumption" 
are fatal. Even some of these might have been cured if 
they had been recognized before the "galloping stage." 

The most common mild cases are those which only show 
a tendency to frequent "catching cold." This is not an 
early symptom, but such patients have the disease in a 
mild form and are the most dangerous to their friends, 
because they usually insist that they have nothing but 
a "bad cold." The best treatment for such patients is 
to go to a consumption specialist once a week, keeping 
a record supplied to them in printed form. The doctor 
can then outline a week's directions in advance. The 
fever record is inspected, the weight taken, and the diet 
prescribed. This is done with good effect in the dispen- 
saries in large cities. Unfortunately, the milder the in- 
fection, the more careless the patient. Only too often, those 
who are sent off for climatic treatment, stop at big hotels 
in large cities and lead lives of dissipation, disregarding the 
rules of health. The fact that over fifteen per cent, of all 
the deaths in California are due to tuberculosis is too elo- 
quent on this point. The worst patients are the too rich 
and the too poor. 

How Cure is Accomplished. — When a tubercle is sur- 
rounded by cells these can grow into a strong wall (Fig. 



332 



PHYSIOLOGY AND HYGIENE 








126), which cuts the nodule off from the rest of the body, leav- 
ing no communication with the blood. -Medicine, therefore, 

cannot reach such a 
spot. Medicine has 
no effect whatever on 
the tubercles. Cer- 
tain medicines can 
make a patient feel 
better, improve his 
appetite, and in this 
way help him in the 
fight. Cough medi- 
cines do harm because 
they allay the very 
irritation which calls 
into play Nature's de- 
fenses. When this 
"healing-in" has 
been accomplished, we 
must do nothing to 
break it down, either by reducing the resistance or by 
exercising the lungs too much. Later this nodule hardens, 
it " calcifies." This cutting off is Nature's "first aid to 
the injured," and if the patient is not careful the wall 
may break down. He must adopt a plan to conserve 
Nature's forces and not hinder them by carelessness and 
by the use of poison drugs. This mode of healing often 
goes hand in hand with an active, ever on-creeping proc- 
ess in the neighborhood, or in other parts of the lung. 
Even after death we can find great areas of healed tubercles. 
At one point the flame may be rapidly fed and burning, and 
in other places the fire is extinct. 



Pig. 126. — Diagram of an old tubercle, with 
dense fibrous wall. 

Various kinds of young fibrous tissue cells at t lie 
top: thickened walls of air spaces of the lung. 
1, Air sac: 2, young cells; 3. fibrous wall; 4, old 
tubercle, broken down. (Highly magnified.) 



RECOGNIZING AND CURING TUBERCULOSIS 333 

How Can We Aid Nature in the Cure of the Disease ? — 
The most important step is building up the body. The 
next, is in the control of the fever. This must never be done 
by taking fever powders; they poison the tissues and rap- 
idly render the patient incurable. If we keep too much 
blood from getting into the neighborhood of the tubercle, 
less of the toxin can be carried away to poison the body. 
If we keep the part quiet and add no further irritation to 
that already there, we prevent dissemination of the infec- 
tion. All this is very easily done by going to bed and 
keeping very quiet, breathing cool, fresh air, the body 
being well covered to keep it warm. Cold air is stronger 
than hot air because heat expands air so that the lungs 
must be filled oftener to satisfy the body. Cold air is also 
fresher, containing a large proportion of pure oxygen. This 
rests the lungs, because they do not have to work so hard 
to furnish oxygen for the red corpuscles. (See page 85.) 
Next to rest and fresh air we need good, wholesome, nu- 
tritious food. This should be selected by the doctor to 
suit each patient. It must be plain, wholesome and 
digestible. 

Climate. — There are certain climates where tuberculous 
patients thrive better than in ordinary climates, especially 
unfavorable are low, damp places where the disease is 
so prevalent. There is no hard and fast rule that can be 
applied to all patients. A climate which helps one con- 
sumptive may be very harmful to another, and here again 
the doctor must decide. No one who has not the means to 
procure the comforts of life should be sent away. It is 
cruel to the patient and unfair to the strangers who have 
to take care of him. As places for treating consumptives 
modern houses, and especially constructed tents and 



334 PHYSIOLOGY AND HYGIENE 

"shacks" are much to be preferred. An inexpensive ar- 
rangement is a "window tent" (Fig. 127). 




Fig. 127.— Window tent. 

Prevention of Tuberculosis. — This comes under two 
heads: 1. The rules to be followed by the consumptive, to 
keep his spittle and his breath, when coughing and sneezing 
from contaminating things from which others may become 
infected. 2. The rules for the well and the puny. These 
have been pretty well gone over. They will be further 
discussed under "general considerations." 

Rules for the Consumptive 

1. He should never spit into anything that cannot be 
burned or disinfected. 

2. He should never cough or sneeze except into a cloth 
or handkerchief which can be burned or boiled. 

3. He should wash his hands, clean his nails and rinse 
his mouth before eating and before mingling with others. 

4. He should cleanse his teeth often and keep his tooth- 
brush where no one can, by mistake, exchange it. 

5. He should never kiss any one under any circumstances. 



RECOGNIZING AND CURING TUBERCULOSIS 335 

6. He should not use any cup, glass, knife, fork or dishes 
used by others; better use paper napkins and burn them. 

7. He should never use any towels or wash goods that 
are used by others. 

8. He should be very careful not to contaminate any- 
thing with the things he uses. 

9. If he have no trained nurse he should see to the boiling 
and disinfecting of contaminated material himself; boiling 
things must be covered while on the fire. 

10. He should never occupy the same bed with another; 
better still to sleep in a separate room. This will also en- 
able him to get the extra ventilation that he needs. 

11. He should keep flies and animals out of his room and 
quarters. 

12. He should have a bare floor to his room and have it 
swept with a bag-broom, moistened with a five-per-cent. 
solution of carbolic acid water; this bag should be boiled or 
renewed often. Dusting should be done with the same care. 

13. All. body discharges, and dressings from sores must 
be disinfected or burned. 

Other precautions, to suit the case, can be prescribed by 
the doctor. 

General Considerations. — Dress. — It is a mistake to 
wrap too warmly in cold weather. The clothing should be 
clean and warm enough to keep one comfortable under all 
conditions. The best authorities are opposed to woolen flan- 
nel or camel's-hair underwear. The clothing next to the 
skin should be such as will absorb moisture and prevent 
its condensation on the surface of the skin. Outer wraps, 
overshoes and heavy clothing, should not be worn indoors. 
Some exercise in tne fresh air on cold days tends to stimu- 
late the surface circulation and obviates the need for very 



336 PHYSIOLOGY AND HYGIENE 

heavy clothing under any conditions. Wrapping up and 
cuddling close to a fire puts a check on the heat-producing 
mechanism of the body. When taking exercise or playing, 
the clothing must be very much lighter, to prevent over- 
heating. Immediately after the exercise additional cloth- 
ing must be put on. The general idea is to stimulate 
heat production in cold weather and pay strict atten- 
tion to the change of outer clothing under varying con- 
ditions. "Taking cold" from chilling comes through the 
skin of the body, either from wet feet, from perspiring body 
or from sudden exposure to cold without sufficient clothing. 
The blood-vessels of the skin contract and the blood-vessels 
of the mucous membrane of the air passages become over- 
filled with blood by a kind of compensation. This affords 
a chance for the bacteria of the nose and throat to become 
active. The heat of a stifling, hot room has no effect on the 
inflamed mucous membrane except to make it feel "stuffy." 
The thing to do is to keep the body warm and breathe fresh 
air. 

Eating. — Food should never be eaten immediately be- 
fore or after violent exercise because then much of the 
blood will be in the blood-vessels of the muscles and the 
lungs. The same blood cannot be made to do extra work 
everywhere at the same time. The same is true about 
eating and bathing. The food should be eaten slowly, and 
then some time allowed for rest. Cold lunches from home 
are preferable to the unwholesome stuff from the nearest 
confectioners, or fruit vendor. Fruit from home can be 
had clean and wholesome, instead of being unripe, over- 
ripe or fly stained and covered with street dust. Remem- 
ber the lesson about washing your hands before eating and 
about not swapping apples, etc., with other children. In 



RECOGNIZING AND CURING TUBERCULOSIS 337 

winter we require three times as much heat-producing food 
as we do in hot weather. The extra food eaten in cold 
weather is burned up in tissues to make heat. For the 
same reason we should take more exercise in cold weather. 

Dwellings. — We are now fairly familiar with the con- 
ditions necessary for a sanitary house. Never enter a closed, 
musty or overheated house, if the dwellers in it refuse to 
open a window. Carpets and straw mattings should not 
be used. Rugs and hangings should be changed often and 
steam cleaned. 

The sleeping quarters should be cool and well ventilated. 
One room can be kept warm to dress in, or a fire built in it 
after rising. It is wrong to think one can take cold in this 
way. A healthy person reacts with a fine glow after a good 
shivering. 

The Defense Against Tuberculosis in the Future. — It has 
taken many hard-working scientists many, many years to 
bring together all the known facts about tuberculosis. We 
are now well over the threshold of a full knowledge of this 
disease. We understand its mode of spread and the meth- 
ods for its prevention. It was because of our lack of knowl- 
edge in former years that the disease has become dissem- 
inated, unhindered, over the entire surface of the earth. The 
disease processes are now understood, the many highways 
and byways of its travel have been searched out. Its 
stealthy methods of undermining the body are known, 
and now the public must learn to understand the lessons 
and assist in helping to 

1. Prevent its occurrence. 

2. Prevent its spreading. 

3. Prevent its making headway after it has entered the 
body. 



338 PHYSIOLOGY AND HYGIENE 

Dr. John H. Pryor has well said: 

"We must care for the consumptive in the right place, 
in the right way, and at the right time until he is cured, 
instead, as now, in the wrong place, in the wrong way, at 
the wrong time until he is dead." 



GLOSSARY 



ACID. — A sour, acrid substance turning litmus paper red. 
ADIPOSE. — Loose connective tissue containing masses of fat cells. 
ALBINO. — A person of pale, milky complexion, with light hair 

and pink eyes. 
ALKALOID. — Intensely bitter, alkaline substances having active 

medicinal or poisonous properties, as morphine, nicotine, 

etc. 
ANESTHETIC. — A medicinal agent, given to prevent or allay 

pain, as ether, chloroform, etc. 
ANEMIA. — The lack of blood in the body, or, in a stricter sense, the 

lack of hemoglobin in the blood. 
ANTISEPTIC. — A substance having the power to prevent putre- 
faction or destroy bacteria. 
APOPLEXY. — The bursting of blood vessels in the brain. 
APPENDICITIS. — An inflammation of the vermiform appendage. 
BACTERIA. — Microscopic, vegetable growths attacking portions 

of the body, producing various diseases. 
BELLADONNA. — A narcotic poison whose active principle, atropia, 

is used to dilate the pupil of the eye. 
BRIGHT'S DISEASE.— A functional disease of the kidneys. 
BRUNNER. — Glands in duodenum, probably secreting pepsin. 
CAFFEIN. — An alkaloid substance from coffee-tree, Paraguay tree, 

etc. 
CATARRH. — An inflammation of a mucous membrane, as of the 

st mach, nose, etc. 
CHYLE.— The milky fluid absorbed by the villi. 
CONVULSION. — A violent agitation of the muscles. 
CORN. — A hardened portion of the epidermis. 
DEGLUTITION.— The process of swallowing. 



340 PHYSIOLOGY AND HYGIENE 

DIABETES. — A disease resulting from an excessive amount of 

sugar in the excretion from the kidneys. 
DIALYSIS. — The separation of a crystalloid from a colloid by 

means of an animal membrane. 
DIETARY. — A table showing the actual amount of food required 

daily to furnish the necessary quantity of foodstuffs. 
DISINFECTANT. — A substance having the power to destroy bacteria. 
DYSPEPSIA.— Indigestion. 

EMMETROPIA.— The normal condition of the eye. 
EMULSION. — Oil suspended in water or other liquid in small 

particles. 
FACET. — An articulating surface of a bone. 
FEVER. — Abnormally heated condition of the body. 
FONTANELLES. — Irregular openings between the bones of the 

cranium. 
GLAND. — A structure consisting of cells and ducts controlled by 

nerves and blood vessels, which secretes a fluid. 
HEMORRHAGE.— Excessive bleeding or loss of blood. 
HASHEESH. — A powerful narcotic from Indian hemp. 
HICCOUGH. — A sudden closing of the glottis while the diaphragm 

is contracting. 
INFLAMMATION. — A painful swelling of any of the tissues caused 

by the accumulation of red corpuscles in the parts affected. 
KARYOKINESIS.— Cell division. 
MALARIA. — An intermittent fever caused by the presence of 

poisonous micro-organisms in the system. 
MUCUS. — A sticky liquid secreted by a mucous membrane. 
NARCOTIC. — A drug that produces stupor or convulsions. 
OSMOSIS. — The process by which liquids and crystalloids pass 

through porous septa. 
PERICHONDRIUM.— A layer of white fibrous connective tissue 

covering cartilage. 
PETROUS BONE.— The hard, bony shell surrounding the middle 

and internal ears. 
PTOMAINE.— (See Alkaloid). 
RICKETS. — Distortion of bones resulting from lack of sufficient 

mineral matter for their proper growth. 



GLOSSARY 341 

RIGOR MORTIS. — (Death stiffening). Commonly supposed to be 
due to clotting of muscle plasma, but more probably due to 
a final severe contraction of muscles induced by the chemical 
changes that bring on death. 

SEROUS MEMBRANE. — A thin epithelial membrane lining the 
visceral cavities, as the pleura, peritoneum, etc. 

TARTAR. — A hard formation on the teeth composed of mucus, 
organic matter, and lime. 

TETANUS. — A continued violent contraction of the muscles making 
certain portions of the body rigid. 

THEIN. — An alkaloid found in tea. 

TRANSFUSION. — The process of injecting blood from the veins 
of one person into those of another. 

UVULA. — The small pendulous body attached to the dorsal portion, 
of the palate. 

VESICLE. — A small baggy or pouched structure. 

VISCERA. — Strictly speaking, any of the vital organs, but com- 
monly the term refers only to the bowels or entrails. 

"WORMIAN BONES. — Small plates in the irregular openings between, 
the bones of the cranium. 



INDEX 



Abdomen, 108. 
Absorption, 126. 

alcohol and, 130. 

changes occurring during, 129. 

in the mouth, 127. 

in the small intestine, 128. 

in the stomach, 127. 

review of, 134. 
Acids, 298. 

Adipose tissue, 38, 133, 136. 
Air cells, 153. 
Albinos, 177. 
Albumens, 131. 
Albuminoids, 111, 138. 
Alcohol, 283. 

as a narcotic, 286. 

as a poison, 286. 

as a stimulant, 281. 

denatured, 278. 

effects on absorption, 130. 

effects on blood, 91. 

effects on blood-vessels, 91. 

effects on digestion, 125. 

effects on excretion, 189. 

effects on heart, 91. 

effects on muscles, 62. 

effects on nervous system, 223. 

effects on respiration, 167. 

effects on senses, 274. 

evils of, 280. 

how made, 277. 

liquors containing, 279. 

moral effects of, 283. 



Alcohol not a food, 284. 

properties and uses of, 274. 
Alimentary canal, 94. 
Alkalies, 300. 
Alveoli, 153. 
Amceba, 8, 93. 
Ammonia, 286. 
Amylopsin, 121, 122, 
Anabolism, 131. 
Anatomy, 2. 
Anemia, 87. 
Animal foods, 145. 
Aorta, 79. 
Apoplexy, 229. 
Aqueous humor, 258. 
Arachnoid, 204, 209. 
Areolar tissue, 37, 133, 177. 
Arteries, 74, 75, 77. 
Assimilation, 131, 134. 
Asthma, 161. 
Astigmatism, 273. 
Auricles, 67. 

Backbone, 25, 27. 
Bacteria, 11, 82. 
Baseball, 55. 
Bathing, 181. 
Beans, 143. 
Bedrooms, 166. 
Beef, 146. 
Biceps, 44. 
Bicuspid valve, 70. 
Bile, 110, 117, 119, 120. 



343 



344 



INDEX 



Bleeding, 81. 


Chyme, 121, 134.. 


Blister, 175. 


Cigarettes, 64, 294. 


Blondes, 177. 


Cilia, 152. 


Blood, 80. 


Ciliary muscles, 262. 


Blood-vessels, 74. 


Circulation, 65. 


Boils, 82. 


Coagulation, 83. 


Bones, 14. 


Cocaine, 290. 


hygiene of, 32. 


Coccyx, 25, 26. 


Bone cells, 34. 


Cochlea, 246. 


Brain, 194. 


Cocoa, 287. 


Bread, 141. 


Coffee, 287. 


Bright 's disease, 172. 


Collar bones, 27. 


Bronchi, 155. 


Color, 265. 


Bronchial tubes, 153. 


Color blindness, 265. 


Bronchioles, 153. 


Common bile duct, 117 120. 


Bronchitis, 161. 


Complexion, 177. 


Brunettes, 177. 


Concha, 243. 


Butter, 148. 


Conjunctiva, 258. 




Connective tissue, 36. 


Caecum, 116. 


Consumption, 12, 162. 


Cancellated bone, 17. 


Cordae tendinse, 70. 


Capillaries, 77. 


Cornea, 258. 


Capsule of Glisson, US. 


Corns, 175. 


Carbohydrates, 136, 139. 


Corpora quadrigemina,. 197. 


Carbon dioxide, 134, 159, 302. 


Corpuscles, 80. 


Cardiac fibers, 43. 


Cortex, 170. 


Carnivorous animals, 140. 


Cow, 124. 


Carpals, 29, 30. 


Cranial nerves, 208. 


Cartilage, 34. 


Cranium, 22, 24, 196. 


Cartilage bones, 15. 


Cream, 149. 


Catabolism, 131, 133 


Cross-eyes, 274. 


Cataract, 273. 


Crura cerebri, 197. 


Cell division, 7. 


Crypts of Lieberkiihn, 115, 121 


Cells, 4. 


Crystalline lens, 259. 


Cement, 95. 


Cuticle, 174, 178. 


Cerebellum, 200. 


Cutis, 173. 


Cerebrum, 199. 




Cheese, 149. 


Deafness, 250. 


Chest, 156. 


Defective hearing, 249. 


Choroid, 256. 


Deglutition, 134. 


Chyle, 122. 


Delirium tremens, 282. 



INDEX 



345 



Denatured alcohol, 278. 
Dermis, 175. 
Dendrons, 192. 
Dentine, 95, 100. 
Diaphragm, 25, 107. 
Diastole, 71. 
Diatoms, 6. 
Digestion, 93. 

in intestine, 121. 

in mouth, 106. 

in stomach, 111. 

review of, 124, 134. 
Diphtheria, 12, 163. 
Disease germs. 12, 111. 
Diseases, v, lo3, 185, 270. 
Drinks, 280. 
Drugs, 276. 
Duodenum, 113. 
Dura mater, 199, 204. 
Dyspepsia, 125. 



Ear, 243, 249. 
Ear bones, 244. 
Eczema. 186. 
Eggs, 148. 
Emulsification, 122. 
Enamel, 95, 100. 
End bulbs, 228. 
Endocardium,. 67. 
Epidermis, 174, 176. 
Epiglottis, 151. 
Epithelium, 95. 
Erysipelas, 12, 185. 
Eustachian tube, 94, 249. 
Excretion, 171. 
Exercise, 52, 220. 
Eye, 252. 
Eyeball, 255. 
Eyebrows. 253. 
Eyelids, 253. 



Fasciculi, 41. 

Fats, 121, 132, 133, 137. 

Fatty degeneration, 63, 91, 193. 

Femur, 28. 

Fibrillar, 41. 

Fibrin, 84. 

Fibrinogen, 83. 

Fibrinoplastin, 83. 

Fish, 147. 

Fontanelles, 25. 

Food, 137. 

Foodstuffs, 137. 

Football, 55, 57. 

Fowls, 147. 

Fractures, 16. 

Freckles, 177. 

Function, 2. 

Fundus, 100. 

Gall-bladder, 118, 119. 
Ganglia, 213. 

of Bidder, 71. 

of Remak, 71. 
Gases, 302. 
Gastric glands, 110. 

juice, 110. 
Gelatine, 18, 111, 138. 
Glands, 3. 
Glycogen, 132, 136. 
Golf, 55. 
Gristle, 35. 
Gullet, 107. 
Gymnastics, 51, 56. 

Habit, 216, 295. 
Hair, 178. 
Harvey, 65. 
Haversian system, 18. 
Hearing, 242. 
Heart, 66. 



346 



INDEX 



Heart bents, 71, 72. 

Heartburn, 110. 

Heat, 160. 

Hepatic veins, 119. 

Herbivorous aiimals, 96, 108, 141. 

Histology, 2. 

Hob-nailed liver, 189. 

Humerus, 29. 

Hyaloid membrane, 259. 

Hydrocarbons, 132, 135, 139. 

Hydrochloric acid, 110, 111. 

Hydrophobia, 59. 

Hygiene, 2. 

and diseases, 9. 

of bones, 32. 

of ears, 250. 

of eyes, 265. 

of muscles, 51. 

of nervous system, 218. 

of skin, 181. 
Hyoid bone, 24, 94, 102. 

Ileo-colic valve, 116. 
Ileum, 113. 
Illusions, 263. 
Images, 260. 
Insalivation, 105. 
Involuntary muscles, 42. 
Intestinal juice, 121. 
Intestines, 113. 
Intoxication, 281. 
Iris, 256. 

Jejunum, 113. 
Joints, 19. 

Kidneys, 169. 

Labyrinth, 245. 
Lachrymal apparatus, 254. 
Lacteals, 89, 115, 122, 128. 
Large intestine, 116. 



Larynx, 36, 95, 151. 

Leucocytes, 82. 

Ligaments, 20, 36. 

Liver, 118, 132, 133, 135, 136. 

Lockjaw, 59. 

Long sight, 271. 

Lungs, 154. 

capacity of, 156. 

diseases of, 161. 
Lymph, 88. 
Lymphatic system, 88. 

Macaroni, 144. 

Madstones, 61. 

Malpighian layer, 174. 

Mastication, 105, 134. 

Measles, 186. 

Meatus, 243. 

Medulla oblongata, 196. 

Meibomian glands, 176, 254. 

Membrane bones, 15. 

Membranes, 3. 

Mesentery, 113. 

Metabolism, 131. 

Metacarpals, 29. 

Metatarsals, 31. 

Midbrain, 197. 

Middle ear, 243. 

Milk, 150. 

Mineral salts, 133, 136, 139. 

Mitral valve, 70. 

Molars, 97. 

Mouth, 94. 

Mucous membrane, 3. 

Muscles, 39. 

Muscular sense, 235. 

Muscular system, 40. 

Mutton, 146. 

Nails, 179. 
Narcotics, 288. 



INDEX 



347 



Narcotic poisons, 302. 
Nerve fibers, 192. 
Nerves, 207. 
Nervous system, 190. 
Neurons, 191. 
Nicotine, 293. 
Nucleus, 4. 

Odors, 240. 

(Esophagus, 107. 

Old sight, 272. 

Olfactory cells, 239. 

Olfactory nerve, 208, 239. - 

Omentum, 109, 110, 113. 

Omnivorous animals, 96, 141. 

Opium, 292. 

Optic mound, 257. 

Optic nerve, 208, 257. 

Organ, 2. 

Organic matter, 159. 

Organs of breathing, 151. 

Organs of circulation, 65. 

Organs of digestion, 93. 

Osmosis, 126. 

Osseous tissue, 14. 

Osteoblasts, 15. 

Osteoclasts, 16. 

Oxidation, 134. 

Oxygen and the blood, 150, 157. 

and combustion, 134. 

and red corpuscles, 81. 

replaces impurities, 85. 

supply decreased, 161, 165, 219. 
Oxyntic cells, 110. 

Pacinian corpuscles, 227. 
Pain, 225. " 

Palpitation of the heart, 92. 
Pancreas, 117. 
Pancreatic duct, 117. 
Pancreatic juice, 113, 120. 



Papillae, 103. 

and taste bulbs, 237. 

of dermis, 174. 

of tongue, 103. 
Papillary muscles, 70. 
Pasteurism, 61. 
Patches of Peyer, 115. 
Peas, 144. 
Pelvis, 28. 
Pepsin, 110. 
Peptic cells, 110. 
Peptones, 111, 121. 
Pericardium, 67. 
Periosteum, 16. 
Peristalsis, 110, 111, 128. 
Peritoneum, 107, 109, 113. 
Permanent teeth, 98. 
Perspiration, 176. 
Perspiratory glands, 176. 
Phalanges, 29, 31. 
Pharynx, 95, 107. 
Physician, 303. 
Physiology, 2. 
Pia mater, 199, 204. 
Plasma, 80, 83. 
Platelets, 83. 
Pleura, 107, 154. 
Pleurisy, 163. 
Plexuses, 213. 
Pneumonia, 164. 
Poisons, 298. 
Pons Varolii, 198. 
Pork, 146. 

Portal circulation, 86. 
Portal vein, 119. 
Potatoes, 143. 

Proteids, 111, 121, 131, 135, 138. 
Protoplasm, 4. 
Ptyalin, 105, 121. 
Pulmonary artery, 85. 
Pulmonary circulation, 85 



348 



INDEX 



Pulmonary veins, 85. 

Pulp, 97. 

Pylorus, 109, 112, 113. 

Rabid dogs, 62, 

Receptaculum chyli, 89, 132, 135. 

Red corpuscles, 80. 

Red marrow, 17. 

Reflex action, 201. 

Rennin, 111. 

Respiration, 150. 

Rest, 221. 

Retina, 257. 

Ribs, 27. 

Rice, 143. 

Rickets, 32. 

Right lymph duct, 89. 

Rods and cones, 257. 

Rods of Corti, 246, 248. 

Sacrum, 26. 

Saliva, 104. 

Salivary glands, 104. 

Sanitation, 9. 

Saponification, 122. 

Sarcolemma, 42. 

Scarlet fever, 188, 249. 

Sclerotic, 255. 

Sebaceous glands, 175, 243. 

Semicircular canals, 245, 248. 

Semilunar valve, 70. 

Sensations, 224. 

Senses, 224. 

Serous membrane, 3. 

Serum, 84. 

Sesamoid bones, 30, 47. 

Short sight, 271. 

Shoulder blades, 27. 

Sight, 252. 

Sinews, 46. 

Skating, 55. 



Skeleton, 22. 
Skin, 173. 
Skull, 22. 
Sleep, 221. 
Small intestine, 113. 
Smallpox, 12, 186. 
Smell, 239. 

Smoker's cancer, 168, 294. 
Soft spot, 25. 
Soups, 151. 

Sphincter muscles, 45, 49, 109, 112. 
Sphenoid, 22. 
Spinal column, 23. 
Spinal cord, 26, 203. 
Spinal nerves, 210. 
Sprains, 57. 

Starches, 106, 121, 136, 139. 
Steapsin, 120, 121. 
Sternum, 27. 
Stimulants, 276. 
Stimuli, 214. 
Stomach, 107, 108. 
Stratum corneum, 174. 
Striated muscles, 41. 
Sugars, 121, 132, 136, 138. 
Sutures, 24. 
•Sweat, 176. 
Sweat glands, 176. 
Swimming, 55. 
Synovia, 19. 

Systemic circulation, 85w 
Systole, 71. 
Sympathetic system, 21 L 

Tactile cells, 227. 
Tarsals, 31. 
Tartar, 100. 
Taste, 237. 
Taste bulbs, 237. 
Tea, 286. 
Tear glands, 254. 



INDEX 



349 



Teeth, 95. 

Temperature, sense of, 234. 
Temporary teeth, 98. 
Tendon of Achilles, 47. 
Tendons, 46. 
Tetanus, 58. 
Thoracic cavity, 109. 
Thoracic duct, 89. 
Tissues, 2. 
Tobacco, 293. 

a bad habit, 295. 

and circulation, 92. 

and digestion, 125. 

and excretion, 189. 

and muscles, 64. 

and nervous system, 223. 

and physical requirements, 297. 

and respiration, 168. 

heart, 92, 294. 
Tongue, 102. 
Tonsils, 103. 
Touch, 227. 
Touch corpuscles, 228. 
Trachea, 151, 152. 
Tricuspid valve, 70. 
Triceps, 44. 
Trunk, 25. 
Trypsin, 120. 
Tympanic membrane, 243. 



Tympanum, 243. 
Typhoid fever, 12, 115 

Uriniferous tubules, 170. 
Unstriated muscles, 42. 

Valvulse conniventes, 115. 

Veins, 76, 79. 

Vena cava, 67, 79. 

Ventilation, 164. 

Ventricles, 67, 68. 

Vermiform appendage, 116. 

Vertebrae, 25. 

Vestibule, 246. 

Villi, 115. 

Vitreous humor, 258. 

Vocal cords, 151. 

Voice, 151. 

Voluntary muscles, 41. 

Walking, 55, 56. 
Water, 133, 136, 159. 
White corpuscles, 82. 
White plague, 162. 
Windpipe, 152. 
Wormian bones, 25. 

Yellow marrow, 17° 
Yellow spot, 257o 



INDEX TO TUBERCULOSIS 
CHAPTERS XXXIII-XXXV 



Age, 321. 

Alcohol and tobacco, 325. 

Bacteria, 306. 

Bacteriology "catching diseases," 
304. 

Biological character of the tu- 
bercle bacillus, 312. 

" Catching" tuberculosis, 320. 



Climate, 333. 

Cost of tuberculosis, 315. 

Constitution, 324. 

Curability of tuberculosis, The, 

330. 
Defense against tuberculosis in 

the future, The, 337. 
Different kinds of bacteria, 307. 



350 



INDEX 



Dwellings, 337. 

Eating, 336. 

Exciting cause, 325. 

General characteristics of bac- 
teria, 309. 

General considerations — dress, 
335. 

Heredity, 323. 

How can we aid nature in the cure 
of the disease? 333. 

How cure is accomplished, 331. 

How diseases are spread, 305 '. 

How the tubercle bacillus gets 
into the body, 315. 

How tuberculosis affects the body, 
317. 

Inoculation, 306. 

Kinds of plants, 308. 

Lesson of the biology of the 
tubercle bacillus, The, 313. 

Locality, 322. 

Meat, 320. 

Milk, 320. 

Mode of spread, 318. 

Nature of tuberculosis, 304. 



Occupation, 325. 

Other diseases as predisposing 
causes, 325. 

Predisposing causes of tubercu- 
losis, 321. 

Prevention of tuberculosis, 334. 

Race, 321. 

Recognizing and curing tuber- 
culosis, 328. 

Role of domestic animals in the 
spread of tuberculosis, 319. 

Route of travel of the bacillus, 
316. 

Rules for the consumptive, 334. 

Servants, mechanics, and la- 
borers, 321. 

Sox. 321. 

Signs and symptoms of tubercu- 
losis, 328. 

Susceptibility, 323. 

Tuberculosis, 304. 

Tubercle bacillus, The, 311. 

Tuberculosis as a disease, 314. 

Toxin of the tubercle bacillus, 330. 

Water— contaminated, 320. 



OCT 1-U91C 



One copy del. to Cat, Div. 

OCT' H 1916 



